Chapter 3 Playing With Numbers Ex 3.1 Solutions
Question - 1 : - Write all the factors of the following numbers:
(a) 24, (b) 15, (c) 21, (d) 27, (e) 12, (f) 20 , (g) 18, (h) 23, (i) 36
Answer - 1 : -
(a) 24 = 1 x 24 = 2 x 12 = 3 x 8 = 4 x 6 = 6 x 4
∴ Factors of 24 = 1, 2, 3, 4, 6, 12, 24
(b) 15 = 1 x 15 = 3 x 5 = 5 x 3
∴ Factors of 15 = 1, 3, 5, 15
(c)21 = 1 x 21 = 3 x 7 = 7 x 3
∴ Factors of 21 = 1, 3, 7, 21
(d)27 = 1 x 27 = 3 x 9 = 9 x 3
∴ Factors of 27 = 1, 3, 9, 27
(e)12 = 1 x 12 = 2 x 6 = 3 x 4 = 4 x 3
∴ Factors of 12 = 1, 2, 3, 4, 6, 12
(f)20 = 1 x 20 = 2 x 10 = 4 x 5 = 5 x 4
∴ Factors of 20 = 1, 2, 4, 5, 10, 20
(g)18 = 1 x 18 = 2 x 9 = 3 x 6
∴ Factors of 18 = 1, 2, 3, 6, 9, 18
(h)23 = 1 x 23
∴ Factors of 23 = 1, 23
(i)36 = 1 x 36 = 2 x 18 = 3 x 12 = 4 x 9 = 6 x 6
∴ Factors of 36 = 1, 2, 3, 4, 6, 9, 12, 18, 36
Question - 2 : - Write first five multiples of:
(a) 5, (b) 8, (c) 9
Answer - 2 : -
(a) 5 x 1 = 5, 5 x 2 = 10, 5 x 3 = 15, 5 x 4 = 20, 5 x 5 = 25
∴ First five multiples of 5 are 5, 10, 15, 20, 25.
(b) 8 x 1 = 8, 8 x 2 = 16, 8 x 3 = 24, 8 x 4 = 32, 8 x 5 = 40
∴ First five multiples of 8 are 8, 16, 24, 32, 40.
(c) 9 x 1 = 9, 9 x 2 = 18, 9 x 3 = ,27, 9 x 4 = 36, 9 x 5 = 45
∴ First five multiples of 9 are 9, 18, 27, 36, 45.
Question - 3 : - Match the items in column 1 with the items in column 2:
Column 1 Column 2
(i)35 (a) Multiple of 8
(ii)15 (b) Multiple of 7
(iii)16 (c) Multiple of 70
(iv)20 (d) Factor of 30
(v)20 (e) Factor of 50
Answer - 3 : - (i) → (b),
(ii) → (d),
(iii) → (a),
(iv) → (f),
(v) → (e)
Question - 4 : - Find all the multiples of 9 up to 100.
Answer - 4 : -
Multiples of 9 up to 100 are:
9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99