Exercise 10 Page 181

Practice makes perfect

We are given the table that shows the times of four runners. We want to find the combined time of Carter and Frater. Let's consider their times.

4 by 100 Meter Times
Runner	Time (s)
Carter	13.4
Frater	12
Bolt	12
Powell	11.7

We will add 13.4 to 12. Before we find the exact sum, we can make an estimate by rounding each addend. We will round 13.4 to 13 because it is the closest whole numbers.

13 + 12 = 25 The sum of 13.4 and 12 is about 25. Now, we can find the exact sum. To add decimals, we line up the decimal points so that place-value positions correspond. We will annex zeros so each place has a digit.

Now, we add the decimals, just as we would with whole numbers, and place the decimal point in the answer.

Our answer 25.4 is really close to our estimation! This means that the combined time of Carter and Frater is 25.4 seconds.

We are given the table that shows the times of four runners. We want to find the difference between Bolt's and Powell's times. Let's consider their times.

4 by 100 Meter Times
Runner	Time (s)
Carter	13.4
Frater	12
Bolt	12
Powell	11.7

We will subtract 11.7 from 12. To subtract decimals, we line up the decimal points so that place-value positions correspond. We will annex zeros so each place has a digit.

Now we subtract the decimals just as we would with whole numbers and place the decimal point in the answer.

The time difference between Bolt and Powell is 0.3 second.

We are given the table that shows the times of four runners. We want to find the combined time of all the runners.

4 by 100 Meter Times
Runner	Time (s)
Carter	13.4
Frater	12
Bolt	12
Powell	11.7

We will add all the times. Let's start by adding up the times that are whole numbers. 12 + 12 = 24

Now, let's add to the result the time of Carter. To find the exact sum, we line up the decimal points so that place-value positions correspond. We will annex zeros so each place has a digit.

Now, we add the decimals, just as we would with whole numbers, and place the decimal point in the answer.

The combined time of Carter, Frater, and Bolt is 37.4 seconds. Next, we will add to this result Powell's time. Once again, we line up the decimal points so that place-value positions correspond.

Finally, we add the decimals, just as we would with whole numbers, and place the decimal point in the answer.

We found that the combined time of all runners is equal to 49.1 seconds.

Subchapter links

Guided Practice p.180

Independent Practice p.181

H.O.T. Problems p.182

Standardized Test Practice p.182-184

Extra Practice p.183

Common Core Review p.184

Exercise 10 Page 181

Hints

Check the answer

Practice exercises

Asses your skill