Q2 of 55 Page 61

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

(a)


(b)

(a) Lets take ‘a’ be the missing number,


So, we have,


2 × a = 6


a = 6/2 = 3


a = 3


So,


2 × 3 = 6


And


5 × a = 10


a = 10/5 = 2


5 × 2 = 10


Missing numbers are 3 and 2.


(b) As we know 60 = 30 × 2


30 = 10 × 3


10 = 5 × 2


Missing numbers are, 2, 5, 3 and 2.


More from this chapter

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7

A number is divisible by 12. By what other numbers will that number be divisible?

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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 isd 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-prime, 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 su,


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

 3

Which factors are not included in the prime factorisation of a composite number?

 4

Write the greatest 4-digit number and express it in terms of its prime factorsd.