Page 21 - Math Smart - 7

1.3.1 Tests of divisibility
O Spotlight
Remember:

Play the divisibility game
on this site.
dividend divisor quotient

.i-z\B
A divisibility test is a quick way of finding out whether a given number is divisible
by a divisor without doing the division calculation. This is usually done by
examining the digits of the dividend.

investigate

Tests of divisibility

Use your knowledge of factors to discover some divisibility rules.
In this investigation you will explore how some numbers are related to their factors.

O Explore 10-, as a factor.
a) Circle each number that has 10 as a factor.

148 25 010 1340 1899 6706 15 595 10 000 15 001 145 890 206 980

b) What do you notice about all the numbers you have circled?

c) Write a divisibility rule for 10. Hint: Look at the last digit of the numbers you have
circled.

d) List 6 five-digit numbers that are divisible by 10. The numbers must not appear in the list
in Question la.

Q Explore 100 as a factor.

a) Circle each number that has 100 as a factor.

200 25 010 1300 1299 8701 13 795 10 000 15 001 265 890 216 900
b) What do you notice about all the numbers you have circled?

c) Write a divisibility rule for 100.

d) List 6 six-digit numbers that are divisible by 100. The numbers must not appear in the list
in Question (2a).

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