1).(1015)2 = ?
(A) 1040125
(B) 1030225 (C) 1050125 (D) 1025125
Answer:(B)
Explanation:
10152 = (1000+15)2 = 10002 + 152 +2 x 1000 x 15
2).Which one is NOT divisible by 3 ?
(A) 5271
(B) 6291
(C) 4372
(D) 8952
Answer:(C)
Explanation: If the total of digits is divisibble by 3, number is also divisible by 3 5271……..5+2+7+1=15 is divisible by 3 6291……..6+2+9+1=18 is divisible by3 4372……..4+3+7+2=16 is not divisible by 3 8952……..8+9+5+2=24 is divisible by 3
3).Largest five digit number exactly divisible by 39 is:
(A) 99979
(B) 99956
(C) 99989
(D) 99996
Answer:(D) Explanation:
Largest 5 digit number is 99999. Let us divide 99999 by 39 39) 99999 (2564 78 ----- 219 195 ----- 249 234 ----- 159 156 ---- 3 From above calculation, we know 39*2564 + 3 = 99999 Therefore 99999-3 = 99996 is the largest divisible number by 39.
4).Which is not the prime number?
(A) 43
(B) 57
(C) 73
(D) 101
Answer:(B)
Explanation: A positive natural number is called prime number if nothing divides it except the number itself and 1. 57 is not a prime number as it is divisible by 3 and 19.
5).103 x 103 + 97 x 97 = ? (A) 21348 (B) 20018 (C) 19648 (D) 21428 Answer: (B) Explanation:
103 x 103 + 97 x 97 = (100+3)2 + (100-3)2 = 2 (1002 + 32 ) [ (X +Y)2 + ( X – Y)2 = 2 ( X2 + Y2 ) ] = 2 (10000 + 9 ) = 2 x 10009 = 20018
6).9848 x 125 = ? (A) 1232000 (B) 1242000 (C) 1231000 (D) 1233000
Answer: (C) Explanation:
9848 x 125 = 9848 x (250 / 2) = 4924 x (500 / 2) = 2462 x (1000 / 2) = 1231 x (1000) = 1231000
7).How many of the following numbers are divisible by 9 96381, 46729, 54459, 85369, 46818
(A) 1 (B) 2 (C) 4 (D) 3 Answer: (D) Explanation: If sum of digits are divisible by 9, number is also divisible by 9
96381…..9+6+3+8+1= 27 (/) 46729…..4+6+7+2+9= 28 (x) 54459…..5+4+4+5+9= 27 (/) 85369…..8+5+3+6+9= 31 (x) 46818…..4+6+8+1+8= 27 (/)
8).What will be the next number? 3, 5, 7, 11, 13, 17…….
(A) 21 (B) 19 (C) 25 (D) 20 Answer: (B) Explanation: This is a sequence of prime numbers