31.
Six bells commence tolling together and toll at intervals of 2, 4, 6, 8, 10 and 12 seconds respectively. In 30 minutes, how many times do they toll together?
• A.
4
• C.
15
• B.
10
• D.
16
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Explanation :

L.C.M. of 2, 4, 6, 8, 10, 12 is 120.

So, the bells will toll together after every 120 seconds, i.e, 2 minutes.

In 30 minutes, they will toll together

 30 2

+ 1    = 16 times

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32.
The H.C.F of 2923 and 3239 is :
• A.
37
• C.
73
• B.
47
• D.
79
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Explanation :

 2923) 3239 (1
 2923
 316 ) 2923 (9
 2844
 79 ) 316 (4
 316
 x

 H.C.F. = 79

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33.
The least number, which when divided by 48, 60, 72, 108 and 140 leaves 38, 50, 62, 98 and 130 as remainders respectively, is:
• A.
11115
• C.
15120
• B.
15110
• D.
15210
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Explanation :

Here (48 - 38) = 10, (60 - 50) = 10, (72 - 62) = 10, (108 - 98) = 10 & (140 - 130) = 10.

 Required number = (L.C.M. of 48, 60, 72, 108, 140) – 10

 = 15120 – 10

 = 15110

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34.
The H.C.F. of two numbers is 11 and their L.C.M. is 7700. If one of the numbers is 275, then the other is:
• A.
279
• C.
308
• B.
283
• D.
318
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Explanation :

 Other number = 11 x 7700 = 308 275

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35.
The least number which should be added to 2497 so that the sum is exactly divisible by 5, 6, 4 and 3 is:
• A.
3
• C.
23
• B.
13
• D.
33