Question

What number should be subtracted from each of the number 23, 30, 57 and 78; so that the remainders are in proportion?

• A. 6
• B. 4
• C. 5
• D. 8

Answer 1

The correct option is A

6

Let the number subtracted be x.

$\therefore$ (23 - x) : (30 - x) : : (57 - x) : (78 - x)

$\frac{23-x}{30-x}=\frac{57-x}{78-x}$

1794 - 101x + $x^2$ = 1710 - 87x + $x^2$

$\Rightarrow$ 14x = 84

$\therefore$ x = 6