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212 lines
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<title>Estimation (Introduction)</title>
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<div id="content" role="main"><!-- #BeginEditable "Body" -->
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<h1 align="center">Estimation (Introduction)</h1>
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<h3 align="center">Estimation is a Skill for Life. </h3>
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<p style="float:right; margin: 0 0 5px 10px;"><img src="images/seagulls.jpg" alt="shopping" width="141" height="300" /></p>
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<p>As you walk around and live your life, imagine if you could easily estimate: </p>
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<ul>
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<li>how much a bill will be, </li>
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<li>which item is the best value for money </li>
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<li>the size, areas and angles of things</li>
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</ul>
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<p>Also, it would be great if you could <b>quickly guess</b> how many people are in a room, how many cars in the street, how many boxes on the shelf, or even how many seagulls on the beach.</p>
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<p>We are not talking exact answers here, but answers that are <b>good enough</b> for your life. </p>
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<h2>Exact vs Estimate</h2>
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<table border="0">
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<tr>
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<td><div class="simple">
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<table border="0" align="center">
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<tr>
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<td width="100"><div align="center" class="huge">=</div></td>
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</tr>
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<tr>
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<td width="100" class="tiny"><div align="center">Equals<br />
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Symbol</div></td>
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</tr>
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</table>
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</div></td>
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<td><p align="left">In mathematics we often stress getting an exact answer. </p>
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<p align="right">But in everyday life a few cents here or there are not going to make much difference ... you should focus on the dollars! </p></td>
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<td><div class="simple">
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<table border="0" align="center">
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<tr>
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<td width="100"><div align="center" class="huge">≈</div></td>
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</tr>
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<tr>
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<td width="100" class="tiny"><div align="center">Approximately<br />
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Equals Symbol</div></td>
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</tr>
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</table>
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</div></td>
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</tr>
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</table>
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<p> </p>
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<p class="larger">Estimation is ...</p>
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<p align="center" class="larger">... finding a number that is <b>close enough</b> to the right answer.</p>
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<ul>
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<div class="bigul">
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<li>You are <b>not</b> trying to get the <b>exact</b> right answer</li>
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<li>What you want is something that is <b>good enough</b> (usually in a hurry!)</li>
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</div>
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</ul>
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<div class="questions"><a href="estimation-game.html">Estimation Games</a></div>
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<h2>Why?</h2>
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<p style="float:right; margin: 0 0 5px 10px;"><img src="../money/images/coin-stack-add.jpg" alt="money" width="106" height="140" /></p>
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<p>Estimation can save you <b>money</b>. Always do a quick estimation of how much you should pay:</p>
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<div class="example">
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<h3>Example: you want to buy five magazines that cost $1.95 each. When you go to buy them the cost is $12.25. Is that right?</h3>
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<p align="center"><i> "five at $1.95 each is about 5 times 2, or about $10" </i></p>
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<p>so $12.25 seems too much!</p>
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<p>Ask to have the total checked.<br />
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</p>
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</div>
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<p style="float:left; margin: 0 10px 5px 0;"><img src="../images/clocks/clock-analog-4.jpg" alt="money" width="122" height="122" /></p>
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<p>Estimation can save you <b>time</b> (when the calculation does not have to be exact):</p>
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<div class="example">
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<h3>Example: you want to plant a row of flowers. The row is 58.3cm long. The plants should be 6cm apart. How many do you need?</h3>
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<p align="center"><i>"58.3 is nearly 60, and 60 divided by 6 is 10, <br />
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so 10 plants should be enough."</i></p>
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</div>
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<p>Estimation can save you from making<b> mistakes with your calculator</b>:</p>
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<div class="example">
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<h3>Example: you are calculating 107 times 56, and the calculator shows this:</h3>
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<p align="center" class="large"><i> 952.00 </i></p>
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<p>Is that right? </p>
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<p align="center"><i>"107 times 56 is a bit more more than 100 times 50, which is 5,000"</i></p>
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<p> </p>
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<p>Ooops! you must have typed something wrong ...</p>
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<p>... in fact you pressed 17×56 (you left out the zero), and without estimating you could have made a really big mistake!</p>
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</div>
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<p><span class="larger">In fact don't trust calculators or computers ... </span></p>
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<p style="float:left; margin: 0 10px 5px 0;"><img src="images/computer-confusion.jpg" alt="Confusion" width="119" height="113" /></p>
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<p class="larger">Computers don't <b>understand</b> what you are doing. </p><p style="float:right; margin: 0 0 5px 10px;"><img src="images/brain-power.jpg" alt="Brain Power" width="120" height="120" /></p>
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<p align="right" class="larger">So use your brain power to <b>double-check</b> everything</p>
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<div style="clear:both"></div>
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<p>And one last important reason:</p>
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<table width="92%" border="0" align="center">
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<tr>
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<td><img src="images/dog-concentrate.jpg" alt="Concentration" width="150" height="125" /></td>
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<td><p class="larger">Estimation helps you <b>focus</b> on what is <b>really going on</b>.</p> </td>
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</tr>
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</table>
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<p> </p>
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<h2>Fun, and Good for your Brain</h2>
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<p>It is actually good fun to do estimating because it keeps your mind active. As you walk around see how good you are at estimating answers before they come up.</p>
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<ul>
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<li>At the supermarket try to add up everything yourself, and then compare it to the final bill</li>
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<li>Estimate how long it will take you to get home</li>
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<li>When shopping, see which is the better bargain by estimating the price per quantity</li>
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<li>and so on!</li>
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</ul>
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<div class="example">
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<h3>Example: You are making invitation cards. It took you 3 minutes and 20 seconds to make one card, but you need to do 15 more ... how long will it take? Think:</h3>
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<p align="center"><i>"... it took a little more than 3 minutes for one card, and 3 × 15 is 45... </i></p>
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<p align="center"><i> ... add a bit more ... maybe <b>50 minutes</b> and I will be done."</i></p>
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<p>And then see how close your estimate was when you finish.</p>
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</div>
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<h2>Skill and Practice</h2>
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<p>Estimating takes skill ... but how do you get this skill?</p>
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<p align="center" class="large">Lots of <b>Practice</b>.</p>
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<p style="float:left; margin: 0 10px 5px 0;"><a href="estimation-game.html" class="large"><img src="images/estimate-multiply.gif" alt="Estimation Game" width="250" height="123" border="0" /></a></p>
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<p> </p>
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<p><span class="larger">So we made some <a href="estimation-game.html">Estimation Games</a> for you to practice with!</span></p><div style="clear:both"></div>
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<p>Practice is the best way to become good at estimating, because you need to develop your own "strategies", as different numbers need different methods:</p>
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<div class="example">
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<h3>Example: </h3>
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<ul>
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<li>550 + 298: <b>298 is nearly 300</b> so an estimate is 550+300 = 850</li>
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<li>550 + 248: <b>50+48 is nearly 100</b> so an estimate is 500+200<b> +100</b> = 800</li>
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</ul>
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<p>In one case it seemed easy to change one number and then add.</p>
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<p>In the other case I added the hundreds together and then increased the result by 100</p>
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</div>
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<p>So the first step is to think <i><b>"how do I go about making this estimate?" </b></i></p>
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<h2>Tips and Tricks</h2>
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<p>After doing some practice, read our page on <a href="estimation-tips-tricks.html">Estimation Tips and Tricks</a></p>
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<h2>Estimating Counts, Lengths and More</h2>
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<p>Estimation is not always about doing calculations.</p>
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<p> It is important for you to be able to estimate how many things you can see, or how long something is or how big something is.</p>
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<div class="example">
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<h3>Example: How many objects are here:</h3>
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<p align="center"><img src="images/estimate-objects.gif" alt="How Many Objects" width="300" height="138" /></p>
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<p>You could count them, but what if you don't need an exact answer, just one that is close enough? Can you guess well? </p>
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<p align="center">Answer: <span class="hide">48</span></p>
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</div>
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<p>Read more on our page on <a href="estimation-visual.html">Visual Estimation</a></p>
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<p> </p>
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<div class="questions">
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<script type="text/javascript">getQ(5837, 5838, 5839, 5840, 5841, 5842, 5845, 5843, 5844, 5846);</script>
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</div>
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<div class="related">
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<a href="estimation-tips-tricks.html">Estimation Tips and Tricks</a>
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<a href="estimation-visual.html">Visual Estimation</a>
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<a href="estimation-game.html">Estimation Games</a>
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<a href="index.html">Numbers Index</a> </div>
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Copyright © 2017 MathsIsFun.com
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