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Janelle is training[br]for a road race.

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Her pedometer tracks how[br]far she runs every day.

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Here are the pedometer readings[br]for the past four

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days: on Saturday, she went[br]3.89 miles; Sunday, 5.1;

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Monday, 10.21; Tuesday, 3.35.

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Estimate the total distance she[br]ran over the four days,

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and then calculate[br]the exact amount.

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Let's estimate first. So I'm[br]just going to round them to

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the nearest mile.

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So 3.89, let's round[br]it up to 4 miles.

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And I'm doing that because in[br]the tenths place, we have an

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8, which is 5 or greater.

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So let's just make that[br]roughly 4 miles.

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Let's make this 5.1.

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We round that down because[br]this 1 is less than 5.

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So let's make this 5 miles.

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10.21, let's make that[br]10 miles because

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2 would round down.

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It's less than 5.

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And 3.35, let's make that 3[br]miles, because 3 is less than

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5, so we'd round down.

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So that is 3 miles.

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And if we were to add them[br]up, 4 plus 5 is 9.

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9 plus 10 is 19.

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19 plus 3 is 22.

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So my estimate is that she ran[br]22 miles over the four days.

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That's my estimate.

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Now let's figure out the exact[br]amount that she ran.

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Let me scroll down[br]a little bit.

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So we're going to have to add[br]3.89 to 5.1-- and remember,

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when you're adding decimals,[br]you want to line up the

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decimal-- 10.21 and[br]then finally 3.35.

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And let's add all of these up.

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Now we'll start in the[br]hundredths place.

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There's nothing here, so 9 plus[br]nothing plus 1 is 10,

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plus 5 is 15.

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So let's write the 5, and then[br]carry, or regroup, the 1.

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Let me do this in[br]another color.

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1 plus 8 is 9.

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9 plus 1 is 10.

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10 plus 2 is 12.

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12 plus 3 is 15.

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Put the 5 down.

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Carry, or regroup, the 1.

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1 plus 3 is 4.

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4 plus 5 is 9.

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9 plus 0 is still 9.

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9 plus 3 is 12.

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Write the 2.

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Regroup this 1 right here.

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I'll do it out here just so it's[br]not part of any of these

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numbers, and then[br]1 plus 1 is 2.

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And then we have to remember[br]the decimal

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sitting right over there.

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So the exact distance she[br]ran was 22.55 miles.

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So our estimate wasn't[br]too bad.

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It was 22 miles.

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We got reasonably close, within[br]about little over a

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half a mile.

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