Playing With Numbers

## EXERCISE 3.5

CBSE Class 6 Maths

**Q1: Which of the following statements are true?**

(a) If a number is divisible by 3, it must be divisible by 9.

(b) If a number is divisible by 9, it must be divisible by 3.

(c) A number is divisible by 18, if it is divisible by both 3 and 6.

(d) If a number is divisible by 9 and 10 both, then it must be divisible by 90.

(e) If two numbers are co-primes, at least one of them must be prime.

(f) All numbers which are divisible by 4 must also be divisible by 8.

(g) All numbers which are divisible by 8 must also be divisible by 4.

(h) If a number exactly divides two numbers separately, it must exactly divide their sum.

(i) If a number exactly divides the sum of two numbers, it must exactly divide the two numbers separately.

Answer:

(a) ✗ (e.g. 15 is divisible by 3 but not by 9)

(b) ✔

(c) ✔

(d) ✔

(e) ✗ (e.g. 8 and 9 are co-primes and none of these are prime. )

(f) ✗

(g) ✔

(h) ✔

(i) ✗

**Q2: Here are two different factor trees for 60. Write the missing numbers.**