Question

The difference in simple interest of a sum invested of Rs.1,500 for 3 years is Rs.18. The difference in their rates is: a) 0.4 b) 0.6 c) 0.8 d) 0.10​

Answer 1

Answer:

Let r

1

and r

2

be the required rate of interest.

Then⇒13.50=

100

1500×3×r

1

−

100

1500×3×r

2

⇒13.50=

100

4500

(r

1

−r

2

)

⇒r

1

−r

2

=

450

135

⇒r

1

−r

2

=

90

27

⇒

10

3

⇒0.3

Answer 2

The difference in their rates is 0.4

Given,

Principal sum invested, P = Rs. 1500

No. of years invested, T = 3 years

Difference between the two simple interest = Rs. 18

To Find,

Difference in their rates

Solution,

This problem could be solved using the following method

We have been given that a sum has been invested for 2 interest rates.

Let the two interest rates be a and b.

We have also been given that the difference between the simple interests for these two interest rates = Rs. 18

Mathematically, the simple interest could be expressed as the following relation:

$\implies SI = \frac{P \times R \times T}{100}$

where P is the principal amount, R is the interest rate, T is the time period.

We have to find the difference between the rates of interest, i.e, a - b.

Therefore, we can write the following relationship:

$\implies 18 = \frac{1500 \times a \times 3}{100} - \frac{1500 \times b \times 3}{100}\\\\\implies 18 = \frac{1500 \times 3}{100} \times (a-b)\\\\\implies 18 = 45 \times (a-b)\\\\\implies a-b = \frac{18}{45}\\\\\implies a-b = 0.4$

Therefore, the difference in their rates is 0.4

Hence, the correct answer is (a) 0.4

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