Question

A man invested Rs. 50000 for 3 years at the compound interest rate of 10% per annum. After 2 years the rate of interest was raised to 10%.
(a) Find the total interest earned by him.
(b) Find the amount he received after 3 years.
(c) Find the amount he received after 10 years if the compound interest rate is of 15%.

Answer 1

Answer:

A) The compound interest earn by man is Rs 70,500

B)  The Amount after 3 years is Rs 120,500

C) The Amount after 10 years is Rs 202,275

Step-by-step explanation:

Given as :

The principal investment amount = P = Rs 50,000

The time period of investment = T = 3 years

The rate of interest = R = 10% compounded

After 2 years The interest raised to 10%

So, After 2 years interest = 10% + 10% = 20 %

Let The Amount after 3 years = Rs A

Let The compound interest earn = Rs c.i

From Compound Interest method

Amount = principal × $(1+\dfrac{rate}{100})^{\textrm time}$

or, A = p × $(1+\dfrac{r}{100})^{\textrm t}$

Or, A = 50,000 × [ $(1+\dfrac{10}{100})^{\textrm 2}$ + $(1+\dfrac{20}{100})^{\textrm 1}$ ]

Or, A = 50,000 × [ (1.1)2 + 1.2 ]

∴ A = Rs 50000 × 2.41

i.e A = Rs 120,500

So, The Amount after 3 years = A = Rs 120,500

Again

∵ Interest = Amount - Principal

or, c.i = A - P

Or, c.i = Rs 120,500 - Rs 50,000

∴ c.i = Rs 70,500

So, The compound interest earn by man =  c.i = Rs 70,500

(C) The interest rate = R' = 15%

The time period = T' = 10 years

Amount after 10 years = A'

Amount = principal × $(1+\dfrac{rate}{100})^{\textrm time}$

or, A' = P × $(1+\dfrac{R'}{100})^{\textrm T'}$

or, A' = 50,000 × $(1+\dfrac{15}{100})^{\textrm 10}$

Or, A' = 50,000 × 4.0455

or, A' = 202,275

So, The Amount after 10 years = A' = Rs 202,275

Hence,

A) The compound interest earn by man is Rs 70,500

B)  The Amount after 3 years is Rs 120,500

C) The Amount after 10 years is Rs 202,275 . Answer