Simple Interest – Scale an amount at the same rate: If Rs 64 amounts to Rs 83.20 in 2 years at simple interest, then at the same rate what will Rs 86 amount to in 4 years?

Introduction / Context:
We first extract the rate from the first scenario, then apply the same simple interest rate to the new principal and time to get the new amount.

Given Data / Assumptions:

• 64 amounts to 83.20 in 2 years → SI over 2 years = 19.20
• Need amount for 86 in 4 years at same rate

Concept / Approach:
From the first case, find yearly SI and rate. Then use A = P * (1 + r * t) for the second case.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

• Other values do not match A = 86 * 1.60.

Common Pitfalls:

• Applying compound growth instead of simple interest.

Final Answer:
Rs 137.60.