Overview Exercise "Loneliness is the most terrible poverty."
- Mother Teresa
11.
5358 x 51 = ?
Answer: A
Explanation:
5358 x 51
= 5358 x (50 + 1)
= 5358 x 50 + 5358 x 1
= 267900 + 5358
= 273258.
12.
The sum of first five prime numbers is:
Answer: E
Explanation:
Required sum = (2 + 3 + 5 + 7 + 11) = 28.
Note: 1 is not a prime number.
Definition: A prime number (or a prime) is a natural number that has exactly two distinct natural number divisors: 1 and itself.
13.
The difference of two numbers is 1365. On dividing the larger number by the smaller, we get 6 as quotient and the 15 as remainder. What is the smaller number ?
Answer: A
Explanation:
Let the smaller number be x . Then larger number = (x + 1365).
x + 1365 = 6x + 15
x = 1350
x = 270
14.
(12)3 x 64 ÷ 432 = ?
Answer: D
Explanation:
Given Exp. =
(12)3 x 64
=
(12)3 x 64
= (12)2 x 62 = (72)2 = 5184
432
12 x 62
15.
72519 x 9999 = ?
A. 725117481 B. 674217481 C. 685126481 D. 696217481 E. None of these
Answer: D
Explanation:
72519 x 9999
= 72519 x (10000 - 1)
= 72519 x 10000 - 72519 x 1
= 725190000 - 72519
= 725117481.
16.
If the number 517 * 324 is completely divisible by 3, then the smallest whole number in the place of * will be:
Answer: A
Explanation:
Sum of digits = (5 + 1 + 7 + x + 3 + 2 + 4) = (22 + x ), which must be divisible by 3.
x = 2.
17.
The smallest 3 digit prime number is:
Answer: B
Explanation:
The smallest 3-digit number is 100, which is divisible by 2.
101 < 11 and 101 is not divisible by any of the prime numbers 2, 3, 5, 7, 11.
Hence 101 is the smallest 3-digit prime number.
18.
Which one of the following numbers is exactly divisible by 11?
Answer: D
Explanation:
(4 + 5 + 2) - (1 + 6 + 3) = 1, not divisible by 11.
(2 + 6 + 4) - (4 + 5 + 2) = 1, not divisible by 11.
(4 + 6 + 1) - (2 + 5 + 3) = 1, not divisible by 11.
(4 + 6 + 1) - (2 + 5 + 4) = 0, So, 415624 is divisible by 11.
19.
(?) - 19657 - 33994 = 9999
Answer: C
Explanation:
19657 Let x - 53651 = 9999
33994 Then, x = 9999 + 53651 = 63650
-----
53651
-----
20.
The sum of first 45 natural numbers is:
Answer: D
Explanation:
Let Sn =(1 + 2 + 3 + ... + 45). This is an A.P. in which a =1, d =1, n = 45.
Sn =
n
[2a + (n - 1)d ]
=
45
x [2 x 1 + (45 - 1) x 1]
=
45
x 46
= (45 x 23)
2
2
2
= 45 x (20 + 3)
= 45 x 20 + 45 x 3
= 900 + 135
= 1035.
Shorcut Method:
Sn =
n (n + 1)=
45(45 + 1)
= 1035.
2
2
x + 1365 = 6x + 15
5x = 1350
