## Wednesday, 7 March 2012

### CBSE Class 6th ( VI) Mathematics Chapter 3. Playing with Numbers :Exercise 3.1

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:
 (a) 24 24 = 1 × 24 24 = 2 × 12 24 = 3 × 8 24 = 4 × 6 Thus, the factors of 24 are 1, 2,3, 4, 6, 8, 12 and 24. (b) 15 15 = 1 × 15 15 = 3 × 5 Thus, the factors of 15 are 1, 3, 5, and 15. (c) 21 21 = 1 × 21 21 = 3 × 7 Thus, the factors of 21 are 1, 3,7 and 21. (d) 27 27 = 1 × 27 27 = 3 × 9 Thus, the factors of 27 are 1, 3,9 and 27. (e) 12 12 = 1 × 12 12 = 2 × 6 12 = 3 × 4 Thus, the factors of 12 are 1, 2, 3, 4, 6 and 12. (f) 20 20 = 1 × 20 20 = 2 × 10 20 = 4 × 5 Thus, the factors of 20 are 1, 2, 4, 5, 10 and 20. (g) 18 18 = 1 × 18 18 = 2 × 9 18 = 3 × 6 Thus, the factors of 18 are 1, 2, 3, 6 and 18. (h) 23 23 = 1 × 23 Thus, the factors of 23 are 1 and 20. (h) 36 36 = 1 × 36 36 = 2 × 18 36 = 3 × 12 36 = 4 × 9 36 = 6 × 6 Thus, the factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18 and 36
2. Write first five multiples of :
 (a) 5 (b) 8 (c) 9
Solution :
 (a) 5 5 × 1 = 5 5 × 2 = 10 5 × 3 = 15 5 × 4 = 20 5 × 5 = 25 Thus, The required first five multiples of 5 are 5, 10, 15, 20 and 25. (b) 8 8 × 1 = 8 8 × 2 = 16 8 × 3 = 24 8 × 4 = 32 8 × 5 = 40 Thus, The required first five multiples of 5 are 8, 16, 24, 32 and 40. (c) 9 9 × 1 = 9 9 × 2 = 18 9 × 3 = 27 9 × 4 = 36 9 × 5 = 45 Thus, The required first five multiples of 5 are 9, 18, 27, 36 and 45.
3. Match the items in column 1 with the items in column 2.
 Column 1 Column 2 35 15 16 20 25 Multiple of  8 Multiple of  7 Multiple of  70 Factor of  30 Factor of  50 Factor of  20
Answer:
 Column 1 Column 2 35 15 16 20 25 (b) Multiple of  7 (d) Factor of  30 (a) Multiple of  8 (f) Factor of  20 (e) Factor of  50