62 Chapter 1 Whole Numbers
c. is divisible by 4, because the number formed by its last two digits is
divisible by 4.d. divisible by 5, because its last digit is 0 or 5.
e.534,840 is divisible by 6, because it is divisible by 2 and 3. (See parts a and b.)
f.534,840 is not divisible by 9, because the sum of its digits is not divisible by 9.
There is a remainder.g.534,84 0 is divisible by 10, because its last digit is 0.24 9 2 R 6
534,84 0
40 4 10
534,8 40
6 Divide whole numbers that end with zeros.
There is a shortcut for dividing a dividend by a divisor when both end with zeros. We
simply remove the ending zeros in the divisor and remove the same number of ending
zeros in the dividend.EXAMPLE (^7) Divide: a. b. c.
StrategyWe will look for ending zeros in each divisor.
WHYIf a divisor has ending zeros, we can simplify the division by removing the
same number of ending zeros in the divisor and dividend.
Solution
There is one zero in the divisor.
a.
Remove one zero from the dividend and the divisor, and divide.
There are two zeros in the divisor.
b.
Remove two zeros from the dividend and the divisor, and divide.
c.To find
we can drop one zerofrom the divisor and the dividend and perform the
division
Thus,9,800 350 is 28.
28
(^35) 980
70
280
280
0
(^35) 980.
(^350) 9,80 0
47,000 100 470 1 470
80 10 8 1 8
80 10 47,000 (^100350) 9,800
Self Check 7
Divide: a.
b.
c.
Now TryProblems 55 and 57
12,0001,500
62,000 100
50 10
7 Estimate quotients of whole numbers.
To estimate quotients, we use a method that approximates both the dividend and the
divisor so that they divide easily. There is one rule of thumb for this method: If
possible, round both numbers up or both numbers down.