What should be subtracted from 30, 56, 40 and 76 so that the remaining numbers may be proportional?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e 4.
Let the number to subtract be x.
(30 - x) : (56 - x) = (40 - x) : (76 - x)
⇒ (30 - x)(76 - x) = (40 - x)(56 - x)
Now
Left side = 30 × 76 - 30x - 76x + x² = 2280 - 106x + x²
Right side = 40 × 56 - 40x - 56x + x² = 2240 - 96x + x²
Now set both sides equal = 2280 - 106x + x² = 2240 - 96x + x²
⇒ 2280 - 106x = 2240 - 96x
⇒ 40 = 10x
⇒ x = 4