Basic Mathematics for College Students

34 Chapter 1 Whole Numbers

WHY Front-end rounding produces whole numbers containing many 0’s. Such

numbers are easier to subtract.

Solution

Both the minuend and the subtrahend are rounded to their largest place valueso

that all but their first digit is zero. Then we subtract the approximations using

vertical form.

The estimate is 85,000.

If we calculate 89,070 5,431, the difference is exactly 83,639. Note that the

estimate is close: It’s only 1,361 more than 83,639.

Round to the nearest ten thousand.

Round to the nearest thousand.

8 9 , 0 7 0

 5 , 4 3 1

→

→

9 0 , 0 0 0

 5 , 0 0 0

8 5 , 0 0 0

Solve application problems by subtracting whole numbers.

To answer questions about how much moreor how many more,we use subtraction.

5

EXAMPLE (^8) Horses Radar, the world’s largest horse, weighs 2,540
pounds. Thumbelina, the world’s smallest horse, weighs 57 pounds. How much more
does Radar weigh than Thumbelina? (Source:Guinness Book of World Records,
2008)
Strategy We will carefully read the problem, looking for a key word or phrase.
WHY Key words and phrases indicate which arithmetic operation(s) should be
used to solve the problem.
Solution
In the second sentence of the problem, the phrase How much moreindicates that
we should subtract the weights of the horses. We translate the words of the problem
to numbers and symbols.
is equal to minus

 2,540  57

Use vertical form to perform the subtraction:

13

Radar weighs 2,483 pounds more than Thumbelina.

2 , 5

4

4

3

0

10

 5 7

2 , 4 8 3

The number of pounds

more that Radar weighs

the weight

of Thumbelina.

the weight

of Radar

The number of pounds

more that Radar weighs

Self Check 8

ELEPHANTSAn average male

African elephant weighs

13,000 pounds. An average male

Asian elephant weighs

11,900 pounds. How much more

does an African elephant weigh

than an Asian elephant?

Now TryProblem 83

Priefert Mfr./Drew Gardner,www.drew.it

Brad Barket/Getty Images

The Language of Mathematics Here are some more key words and phrases

that often indicate subtraction:

loss decrease down backward fell less than fewer

reduce remove debit in the past remains declined take away