Exercise: Numbers

Questions for: Numbers

If x and y are the two digits of the number 653xy such that this number is divisible by 80, then x + y = ?
A:
2 or 6
B:
4
C:
4 or 8
D:
8
Answer: A

80 = 2 x 5 x 8

Since 653xy is divisible by 2 and 5 both, so y = 0.

Now, 653x is divisible by 8, so 13x should be divisible by 8.

This happens when x = 6.

x + y = (6 + 0) = 6.

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If 60% of 3 of a number is 36, then the number is:
5
A:
80
B:
100
C:
75
D:
90
Answer: B

Let the number be x. Then

60% of 3 of x = 36
5

60 x 3 x x = 36
100 5

x = 36 x 25 = 100
9

Required number = 100

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On multiplying a number by 7, the product is a number each of whose digits is 3. The smallest such number is:
A:
47619
B:
47719
C:
48619
D:
47649
Answer: A

By hit and trial, we find that

47619 x 7 = 333333.

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2056 x 987 = ?
A:
1936372
B:
2029272
C:
1896172
D:
1926172
Answer: B
2056 x 987 = 2056 x (1000 - 13)
= 2056 x 1000 - 2056 x 13
= 2056000 - 26728
= 2029272.
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If the number 91876 * 2 is completely divisible by 8, then the smallest whole number in place of * will be:
A:
1
B:
2
C:
3
D:
4
Answer: C

Then number 6x2 must be divisible by 8.

   x = 3, as 632 is divisible 8.

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