H.C.F and L.C.M

Q11. If two numbers are in the ratio 7:5 and their L.C.M is 315, then their sum is
(a) 108
(b) 123
(c) 135
(d) 141

Q12. The least perfect square number which is divisible by 4, 5, 6 and 8 is
(a) 3200
(b) 3400
(c) 3600
(d) 3800

Q13. The smallest number which is divisible by 12, 15, 25 and is a perfect square is
(a) 3100
(b) 3350
(c) 3500
(d) 3600

Q14. The traffic lights at three different road crossing change after every 48 seconds, 72 seconds and 108 seconds respectively. If they all change simultaneously at 8.20 hours, then at what time will they again change simultaneously ?
(a) 8.22.15 hrs
(b) 8.27.12 hrs
(c) 8.28.35 hrs
(d) 8.30.30 hrs

Q15. An electronic device makes a beep after every 60 sec. Another device makes a beep after every 62 sec. They beeped together at 10 a.m. The next time, when they would beep together at the earliest
(a) 10.31 am
(b) 10.39 am
(c) 10.46 am
(d) 10.51 am

Q16. What is the least number which when divided by 9, 12, 15 leaves a remainder 2 in each case ?
(a) 182
(b) 189
(c) 197
(d) 201

Q17. Six bells commence tolling together and toll at intervals of 2, 4, 6, 8, 10, 12 seconds respectively. In 30 minutes, how many times do they toll together ?
(a) 16 times
(b) 19 times
(c) 21 times
(d) 24 times

Q18. The L.C.M of two prime numbers a and b (a > b) is 161. The value of 2a - b is
(a) 29
(b) 32
(c) 39
(d) 43

Q19. Six bells commence tolling together and toll at intervals of 2, 4, 6, 8, 10, 12 seconds respectively. In 28 minutes, how many times do they toll together.
(a) 11 times
(b) 12 times
(c) 15 times
(d) 19 times

Q20. The ratio between two numbers is 4:5. If their L.C.M is 180, then the numbers are
(a) 14, 24
(b) 16, 38
(c) 30, 42
(d) 36, 45


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