Numbers

Squares
1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225, 256, 289, 324, 361, 400, 441, 484, 529, 576, 625, 676, 784, 841, 900

Cubes
1, 8, 27, 64, 125, 216, 343, 512, 729, 1000

Fractions


Divisibility Rules
Divisibility by 2 : if the number end in an even number
Divisibility by 3 : if the sum of the digits of the number is divisible by 3
Divisibility by 4 : if the number formed by the last two digits of the number is divisible by 4.
Divisibility by 5 : if the last digit of the number is either 0 or 5.
Divisibility by 6
Divisibility by 7
Divisibility by 8
Divisibility by 9
Divisibility by 10
Divisibility by 11
Divisibility by 13
Divisibility by 17
Divisibility by 19

Solved Problems

1. When 75 is added to 75% of a number, the answer is the number. Find 40% of that number. [CGL, 2013]
(a)100 (b)80 (c)120 (d)160
A. Let the number be 'x'. Then, 75% of the number is 0.75x. Therefore, 0.75x+75=x; x=300. Finally 40% of 300 is 120.