Exercise 7F
Question 1
1. Find the LCM of each of the following by listing multiples.
(i) 12,16
(ii) 15,25
(iii) 8,9
(iv) 2, 4 and 6
(v) 5,8 and 10
2. Find the LCM of each of the following by prime factorisation method.
(i) 14,24
(ii) 12,20 and 36
(iii) 42,63 and 140
(iv) 8,40,56,60
(v) 18,36,45 and 50
3. Find the LCM of each of the following by division method.
(i) 16,24 and 40
(ii) 26,32,65 and 80
(iii) 72,120,150 and 135
(iv) 33,54,132 and 140
(v) 9,12,45 and 60
2. Find the least number which is exactly divisible by 20,28 and 32 ?
5. What will be the least number which when divided by 12,21 and 35 leaves a remainder 6 in each case?
6. Find the least number of 5 -digits exactly divisible by each of 3,4,5,6,7 and 8 .
7.Three brands A, B and C of biscuits are available in packets of 12,15 and 21 biscuits respectively. If a shopkeeper wants to buy an equal number of biscuits of each brand, what is the minimum number of packets of each brand he should buy?
8. In a firing range, 4 shooters are firing at their respective targets. The first, the second, the third and the fourth shooter hit the target once in every 5s, 6s, 7s and 8s respectively (s = seconds). If all of them hit their target at 9 : 00 a.m., when will they hit their target together again?
Multiple Choice Questions (MCQs)
Tick (✔) the correct option
9. The LCM of two co-prime numbers is equal to
(a) 1
(b) the greater number
(c) their product
(d) odd
10. The greatest number of three digits exactly divisible by 12,16 and 24 is
(a) 994
(b) 960
(c) 980
(d) 972
11. Three planets revolve round the Sun once in 200,250 and 300 days respectively in their own orbits. When do they all come relatively to the same position at a certain point of time in their orbits?
(a) After 3000 days
(b) After 2000 days
(c) After 1500 days
(d) After 1200 days
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