UPSC Civil Services 2014 Prelims General Studies Paper II

Let no. of column = x, no. of rows = y
∴ xy = 630 - [3 × 1 + 3 × 2 + ......... + 3 × (y – 1)]
= 630 – 3 [1 + 2 + ........ + (y – 1)]
xy=630−

3(y−1)y

2

(a) If y=3, then 3x=630−9 ⇒x=

621

3

=207
(b) If y=4, then 4x=630−18 ⇒x=

612

4

=153
(c) If y=5, then 5x=630−30 ⇒x=

600

5

=120