Notes of chapter: Playing with Numbers are presented below. Indepth notes along with worksheets and NCERT Solutions for Class 8.
Tests of divisibility
(i) Numbers are divisible by 10 if ones digit of a number is 0.
Eg:- 20, 30 ,40…
(ii) Numbers are divisible by 5 if ones digits are alternately 5 and 0.
Eg:- 5, 10, 15, 20….
(iii) Numbers are divisible by 2 if ones digit is 0, 2, 4,6 or 8.
Eg:- 10, 12, 14, 16, 18…
(iv) A number is divisible by 9 if the sum of its digits is divisible by 9. Otherwise it is not divisible by 9.
Eg:- Check if 108 is divisible by 9.
Ans-
Sum of digit of the number 108 = 1 + 0 + 8
= 9
9 is divisible by 9.
Hence, 108 is divisible by 9.
(v) A number is divisible by 3 if the sum of its digits is divisible by 3. Otherwise it is not divisible by 3.
Eg:- Check if 108 is divisible by 3.
Ans-
Sum of digit of the number 108 = 1 + 0 + 8
= 9
9 is divisible by 3.
Hence, 108 is divisible by 3.
Helping Topics