How long (in years) will it take for ₹1,680 to become ₹2,100 at a rate of 4% per annum simple interest?

Correct option is A

Given:

Principal P = 1,680

Amount A = 2,100

Rate of interest R = 4% per annum

We need to find the time t in years.

Formula Used:

Amount = P + SI

SI = $$\frac{P \times R \times t}{100}$$​​

Solution: 

SI = 2100 - 1680 = 420 

Now, Using the SI formula;

​$$420 = \frac{1,680 \times 4 \times t}{100} \\ \ \\420 = \frac{6,720 \times t}{100}\\ \ \\42,000 = 6,720 \times t \\ \ \\t = \frac{42,000}{6,720} = 6.25 \text{ years}$$​​

Thus, it will take 6.25 years for ₹1,680 to become ₹2,100 at a rate of 4% per annum simple interest.