1. A sum of money placed at compound interest doubles itself in 4 years. In how many years will it amount to 8 times?
1. 10 years
2. 8 years
3. 6 years
4. 12 years
Answer & Explanation Answer:- 4 Explanation :- Let P = Rs.100 Rate = R% A = Rs. 200 Time = 4 years. 2. On what sum will the compound interest for 2 1⁄2 years at 10% amount to Rs. 31762.5? Answer & Explanation Answer:- 3 Explanation :- = [ P(1+10/100)^2 ] [ (1+10/200)^T ] = Rs. 31762.5 3. The compound interest on Rs. 20,000 at 8% per annum is Rs. 3,328. What is the period (in year)? Answer & Explanation Answer:- 4 Explanation :- Let the period be t years. 4. A man borrows Rs. 20,000 at 10% compound interest. At the end of every year he pays Rs. 2000 as part repayment. How much does he still owe after three such installments? Answer:- 3 Explanation :- Principal (For 1st year)= Rs. 12500 5. The present worth of Rs. 242 due in 2 years at 10% per annum compound interest is: Answer & Explanation Answer:- 4 Explanation :- Present worth of Rs. x due T years hence is given by
Then , A = P*[1+ (r/100)]n
200 = 100*[1+(R/100)]4
2 = [1+(R/100)]4 ————- (1)
If sum become 8 times in the time T years,
Then,8 = (1+(R/100))T
23 = (1+(R/100))T ————- (2)
By putting value of 2 from equation (1) in equation (2)
([1+(R/100)]4)3 = (1+(R/100))T
[1+(R/100)]12 = (1+(R/100))T
Thus, T = 12 years.
1. Rs.5000
2. Rs.20000
3. Rs.25000
4. Rs.30000
P [(11/10)^2] × (21/20) = 31762.5
P = (31762.5×20×10×10) / (21×11×11) = (1512.5×20×10×10)/(11×11)
P = (137.5×20×10×10)/11 =12.5×20×10×10 = Rs. 25000
1. 1 year
2. 4 years
3. 3 years
4. 2 years
Amount after t years = Rs.20000 + Rs.3328 = Rs. 23328
P(1+R/100)^T = 23328
20000(1+8100)^T = 23328/20000
(108/100)^T = 23328/20000
(11664/10000) = (108/100)^2
(108/100)^T = (108/100)^2
Therefore, T = 2 years
1. Rs.24000
2. Rs.15000
3. Rs.20000
4. Rs.10000
Therefore Interest (for 1st year) = 20% of 12500 = Rs. 2500
Amount paid At the end of 1st year = Rs. 2000
Therefore , Principal (for 2nd year) = 12500 +2500 – 2000 = 13000
Therefore Interest (for 2nd year) = 20% of 13000 = Rs. 2600
Amount paid At the end of 2nd year = Rs. 2000
Therefore , Principal (for 3rd year) = 13000 +2600 – 2000 = 13600
Therefore Interest (for 3rd year) = 20% of 13600 = Rs. 2720
Amount paid At the end of 3rd year = Rs. 2000
Therefore , Amount after three installments = 13600 +2720 – 2000 = Rs.14320
1. Rs. 180
2. Rs. 240
3. Rs. 220
4. Rs. 200
Present Wort = x/ [ (1+R/100)^T]
Present Worth = 242/ [(1+10/100)^2] = 242 / [(11/10)^2] = Rs. 200