Rakesh invests a sum of ₹5,000 and Shivam invests a sum of ₹9,000 at the same rate of simple interest per annum. If, at the end of 3 years, Shivam gets ₹360 more interest than Rakesh, then find the rate of interest per annum (in percentage).

Question

Question

This question was previously asked in

RRB NTPC Graduate Level CBT-I Official Paper (Held On: 09 Jun, 2025 Shift 1)

Answer 1

Given:

Principal invested by Rakesh (P_R) = ₹5,000

Principal invested by Shivam (P_S) = ₹9,000

Time (t) = 3 years

Difference in interest = ₹360

Formula used:

Simple Interest (SI) = P × r × t / 100

Difference in interest = SI_S - SI_R

Calculations:

SI_S = PR × r × t / 100

SI_R = PS × r × t / 100

Difference in interest = ₹360

⇒ (PS × r × t) / 100 - (PR × r × t) / 100 = ₹360

⇒ r × t × (PS - PR) / 100 = ₹360

⇒ r × 3 × (₹9,000 - ₹5,000) / 100 = ₹360

⇒ r × 3 × ₹4,000 / 100 = ₹360

⇒ r × ₹12,000 / 100 = ₹360

⇒ r × ₹120 = ₹360

⇒ r = ₹360 / ₹120

⇒ r = 3%

∴ The rate of interest per annum is 3%, and the correct answer is option (2).