- 5
- 15
- 8
- 5.6

Option 1 : 5

__Shortcut Trick__

Sum of two rates = {(Sum of SI at different rates) × 100}/(Principal × Time)

Sum of the rates = (400 × 100)/(2000 × 4)

⇒ 40000/8000 = 5

**∴ The sum of interest rates is Rs. 5.**

**Traditional method:**

Given:

Principal and Time in each case is Rs. 2000 and 4 years respectively

The Sum of S.I. = Rs. 400

Formula used:

S.I. = (Principal × Rate × Time)/100

Calculation:

Let R1 and R2 be the interest rate of each investment, (R1 > R2)

According to the question,

{(2000 × R1 × 4)/100} + {(2000 × R2 × 4)/100} = 400

⇒ 80R1 + 80R2 = 400

⇒ 80(R1 + R2) = 400

⇒ (R1 + R2) = (40/8) = 5.

∴ The sum of interest rates is Rs. 5.

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