Exercise: Numbers

Questions for: Numbers

(12345679 x 72) = ?
A:
88888888
B:
888888888
C:
898989898
D:
9999999998
Answer: B
12345679 x 72 = 12345679 x (70 +2)
= 12345679 x 70 + 12345679 x 2
= 864197530 + 24691358
= 888888888
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The smallest prime number is:
A:
1
B:
2
C:
3
D:
4
Answer: B
The smallest prime number is 2.
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8597 - ? = 7429 - 4358
A:
5426
B:
5706
C:
5526
D:
5476
Answer: C 
 7429          Let 8597 - x = 3071
-4358          Then,      x = 8597 - 3071
 ----                       = 5526
 3071
 ----
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A 3-digit number 4a3 is added to another 3-digit number 984 to give a 4-digit number 13b7, which is divisible by 11. Then, (a + b) = ?
A:
10
B:
11
C:
12
D:
15
Answer: A 
 4 a 3  |
 9 8 4  }  ==> a + 8 = b  ==>  b - a = 8  
13 b 7  |

Also, 13 b7 is divisible by 11      (7 + 3) - (b + 1) = (9 - b)

  (9 - b) = 0

  b = 9

(b = 9 and a = 1)     (a + b) = 10.

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How many 3 digit numbers are divisible by 6 in all ?
A:
149
B:
150
C:
151
D:
166
Answer: B

Required numbers are 102, 108, 114, ... , 996

This is an A.P. in which a = 102, d = 6 and l = 996

Let the number of terms be n. Then,

a + (n - 1)d = 996

   102 + (n - 1) x 6 = 996

   6 x (n - 1) = 894

   (n - 1) = 149

   n = 150.

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