Class 8 Maths

# Comparing Quantities

## Exercise 8.3

Question 1: Calculate the amount and compound interest on

(a) Rs 10,800 for 3 years at 12.5% per annum compounded annually.

(b) Rs 18,000 for 2.5 years at 10% per annum compounded annually.

(c) Rs 62,500 for 1.5 years at 8% per annum compounded half yearly.

(d) Rs 8,000 for 1 year at 9% per annum compounded half yearly.

(e) Rs 10,000 for 1 year at 8% per annum compounded half yearly.

Alternate method: Calculating big multiplication can be tedious. Compound interest can also be calculated by finding yearly amount for each year separately.
1st half year 10000+400=10400
2nd half year 10400+416=10816

Question 2: Kamala borrowed Rs 26,400 from a Bank to buy a scooter at a rate of 15% p.a. compounded yearly. What amount will she pay at the end of 2 years and 4 months to clear the loan?

Solution: Amount after 1st year 26400 + 3960 = 30360
Amount after 2nd year 30360 + 4554 = 34914
To make things easier interest can be bifurcated into two parts of 10% and 5% as follows:
1st year 26400 + 2640 + 1320 = 30360
2nd year 30360 + 3036 + 1518 = 34914

Question 3: Fabina borrows Rs 12,500 at 12% per annum for 3 years at simple interest and Radha borrows the same amount for the same time period at 10% per annum, compounded annually. Who pays more interest and by how much?

Interest for Radha = 16637.50-12500=4137.50
Interest paid by Fabina is Rs. 362.50 more than that paid by radha

Question 4: I borrowed Rs 12,000 from Jamshed at 6% per annum simple interest for 2 years. Had I borrowed this sum at 6% per annum compound interest, what extra amount would I have to pay?

Solution: The extra amount payable would be interest on the first year’s interest
1st year’s interest = 12000 x 6%=720
Interest on 720 = 720 x 6%=43.20
Extra amount payable = Rs. 43.20

Question 5: Vasudevan invested Rs 60,000 at an interest rate of 12% per annum compounded half yearly. What amount would he get

(i) after 6 months?

Solution: Amount = 60000+60000 x 6%=60000+3600=63600

(ii) after 1 year?

Solution: Amount = 63600+63600 6% = 63600+3816=67416