Question

The compound interest on certain sum for 2 years at 5% is 51.25 rupee. Find the simple interest for 3 year at the same rate of interest. 
1. 60
2. 90
3. 75
4. 72

Answer 1

Correct Answer - Option 3 : 75

Given: 

C.I for 2 years at 5% rate of interest is 51.25 rupee.

Concept: 

For 1^st year 

Simple interest and compound interest are equal.

If the simple interest of first-year is 'I' then C.I for 2 year 

C.I = [I + I + (I × R%)]

Calculation: 

Let the simple interest for the first year is 'Z'

Now, 

⇒ [Z + Z + (Z × 5%)] = 51.25

⇒ 2Z + Z/20 = 51.25

⇒ 41Z = 51.25 × 20

⇒ Z = 1025/41

⇒ Z = 25

So,Simple interest for first year is 25.

Simple interest for 3 years at the same rate percent

⇒ 3 × 25

⇒ 75

∴ The required S.I for 3 years is 75.