If a and b are odd numbers, then which of the following is even?
a + b + ab
a + b - 1
a + b + 1
a + b + 2ab
216 - 1 is divisible by
11
13
17
19
C.
17
216 - 1 = (28)2 - 1
= (28 + 1) (28 - 1)
= (256 + 1) (256 - 1)
= 257 x 255 which is exactly divisible by 17.
What is the least number which when divided by 5, 6, 7, 8 gives the remainder 3 but is divisible by 9?
1463
1573
1683
1793
The HCF and LCM of two numbers are 12 and 924 respectively. Then the number of such pairs is
0
1
2
3