A sum of ₹2,400 is invested for 4 years at R% p.a, simple interest and the simple interest received is ₹1,152. Find the amount received after 3 years when the same sum is invested at (R + 8) % p.a, simple interest.

A sum of ₹2,400 is invested for 4 years at R% p.a, simple interest and the simple interest received is ₹1,152.

$$simple\ interest=\frac{principal\times\ rate\times\ time}{100}$$

$$1152=\frac{2400\times R\times\ 4}{100}$$

R = 12%

Amount received after 3 years when the same sum is invested at (R + 8) % p.a, simple interest = $$principal+\frac{principal\times\ rate\times\ time}{100}$$

= $$2400+\frac{2400\times\ \left(12+8\right)\times3}{100}$$

= $$2400+\frac{2400\times\ 20\times3}{100}$$

= 3840