Calculate the amount and compound interest on

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

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

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

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

(You could use the year by year calculation using SI formula to verify).

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

Amount on Compound Interest is given by the formula,

and Compound interest can be calculated by the formula
C.I = Amount - Principal
where,
P = Principal Amount
r = rate of interest
n = time (in years)
(a) Here, Principal (P) = Rs. 10800, Time (n) = 3 years,

Rate of interest (R) = 12 1/2 % = (25/2)%

= Rs. 15,377.34

Compound Interest (C.I.) = A – P

= Rs. 15377.34 - Rs. 10800  = Rs. 4,577.34

(b) Here, Principal (P) = Rs. 18,000, Time (n) =  years, Rate of interest (R) = 10% p.a.

  [For 2 years]

= Rs. 21,780

Interest for 1/2 years on Rs. 21,780 at rate of 10% = 

= Rs. 1,089

Total amount for  years

= Rs. 21,780 + Rs. 1089 = Rs. 22,869

Compound Interest (C.I.) = A – P

= Rs. 22869 – Rs. 18000 = Rs. 4,869

(c) Here, Principal (P) = Rs. 62500, Time (n) = 3/2 years =  ½(3) years = 3 (compounded half yearly)

Rate of interest (R) = = 4% (compounded half yearly)

Amount (A)

= Rs. 70,304

Compound Interest (C.I.) = A – P

= Rs. 70304 – Rs. 62500 = Rs. 7,804

(d) Here, Principal (P) = Rs. 8000, Time (n) = 2×½ years = 2(compounded half yearly)

Rate of interest (R) = half of 9% = (compounded half yearly)

Amount (A)

= Rs. 8,736.20

Compound Interest (C.I.) = A – P

= Rs. 8736.20 – Rs. 8000

= Rs. 736.20

(e) Here, Principal (P) = Rs. 10,000, Time (n) = 1 years = 2 years (compounded half yearly)

Rate of interest (R) = 8% = 4% (compounded half yearly)

= Rs. 10,816

Compound Interest (C.I.) = A – P

= Rs. 10,816 – Rs. 10,000 = Rs. 816