Final answer:
To determine the time required for ₹ 4200 to become ₹ 5040 at 8% per annum, calculate the interest earned (₹ 840) and use the simple interest formula, resulting in 2.5 years.
Step-by-step explanation:
To calculate the time in years it will take for a sum of ₹ 4200 to yield an amount of ₹ 5040 at 8% per annum, we can use the simple interest formula:
Interest (I) = Principal (P) × Rate (R) × Time (T)
First, we need to find out the total interest earned, which is the difference between the amount at the end and the original principal:
₹ 5040 - ₹ 4200 = ₹ 840
Now, using the simple interest formula and plugging in the values, we get:
₹ 840 = ₹ 4200 × 0.08 × T
To find the time (T), we need to rearrange the equation for T :
T = Interest / (Principal × Rate)
T = ₹ 840 / (₹ 4200 × 0.08)
T = ₹ 840 / ₹ 336
T = 2.5 years
So, it will take 2.5 years for the sum of ₹ 4200 to grow to ₹ 5040 at an annual interest rate of 8%.