Practice MCQ Questions and Answer on Number System
611.
The sum of all natural numbers from 75 to 97 is -
(A) 1598
(B) 1798
(C) 1958
(D) 1978
Solution:
The sum of all natural numbers upto 97 - sum of all natural numbers upto 74 sum of n natural numbers
612.
Let x = (633)24 - (277)38 + (266)54. What is the units digits of x?
(A) 8
(B) 6
(C) 4
(D) 7
Solution:
x = (633)24 - (277)38 + (266)54 x = 1 - 9 + 6 x = 7 - 9 x = . . . . . 7 - 9 x = 17 - 9 x = 8
613.
Find the remainder when 67107 is divided by 7.
(A) 4
(B) 2
(C) 1
(D) 6
Solution:
614.
A gardener plants his garden with 5550 trees and arranged them so that there is one plant more per row as there are rows then number of trees in a row is:
(A) 56
(B) 74
(C) 76
(D) 75
Solution:
Let there be n rows, then number of trees in each row = (n + 1) Thus, total number of trees, n × (n +1) = 5550 Now, at this moment this problem can be solved in two ways. First by finding the roots of quadratic equation. Second, by using the values from options. 74 × 75 = 5550 i.e. (n + 1) = 75
615.
The number 89715938* is divisible by 4. The unknown non-zero digit marked as * will be :
(A) 2
(B) 3
(C) 4
(D) 6
Solution:
Let the missing digit be x. Then, (80 + x) must be divisible by 4. Hence, x = 4
616.
In a certain series, each number except the first and second is obtained by adding the previous two numbers. If the first no is 2 and sixth no is 26, then the seventh number is:
If sum of two numbers be a and their product be b, then the sum of their reciprocals is :
(A) +
(B)
(C)
(D)
Solution:
Let the two number are P and Q P + Q = a PQ = b ⇒ + ⇒ ⇒
618.
Which of the following fraction is the smallest ?
(A)
(B)
(C)
(D)
Solution: Step 1 : Compare two fractions ⤩ Cross multiply 63 , 42 ↑ ↑ ⤩ 42 is smaller than 63 So, is smaller than Step 2 : Compare (i) (ii) ⤩ Cross multiply it 35 , 36 ↑ ↑ ⤩ 35 is smaller than 36 So, is smaller than Step 3 : Compare (i) (ii) ⤩ Cross multiply it 49 , 45 ↑ ↑ ⤩ 45 is smaller than 49 S0, is the smallest Alternate :
619.
Find the least number which will leaves remainder 5 when divided by 8, 12, 16 and 20.
(A) 240
(B) 245
(C) 265
(D) 235
Solution:
We have to find the Least number, therefore we find out the LCM of 8, 12, 16 and 20. 8 = 2 × 2 × 2; 12 = 2 × 2 × 3; 16 = 2 × 2 × 2 × 2; 20 = 2 × 2 × 5; LCM = 2 × 2 × 2 × 2 × 3 × 5 = 240; This is the least number which is exactly divisible by 8, 12, 16 and 20 Thus, Required number which leaves remainder 5 is, 240 + 5 = 245
620.
A number divided by 68 gives the quotient 260 and remainder zero. If the same number is divided by 65, the remainder is :
(A) 0
(B) 1
(C) 2
(D) 3
Solution:
Number = (68 × 260) = 17680 On dividing this number by 65, we get zero as remainder