SSC MTS 5 Aug 2019 Shift 1 Paper

Short Trick:
let the amount be Rs. x, then
750/x = 900/750
⇒ x = (750 × 750)/900
⇒ x = 625
Detailed Solution:
A = 750, t = 1 year
As we know,
A = P (1 + r/100)${}^{\mathrm{t}}$
⇒ 750 = P (1 + r/100)
⇒ 750/(1 + r/100) = P ---(1)
Again,
A = 900, t = 2 year
As we know,
900 = P (1 + r/100)${}^2$
⇒ 900 = P (1 + r/100)${}^2$
P = 900/(1 + r/100)${}^2$ ---(2)
From equation (1) and equation (2)
750/(1 + r/100) = 900/(1 + r/100)${}^2$
⇒ (1 + r/100)${}^2$/(1 + r/100) = 900/750
⇒ (1 + r/100) = 6/5
⇒ r/100 = 6/5 – 1
⇒ r/100 = 1/5
⇒ r = (1/5) × 100
⇒ r = 20%
Now,
750 = P (1 + 20/100)
⇒ 750 = P × 6/5
⇒ P = 750 × (5/6)
⇒ P = 625