Q1.
A sum of money placed at compound interest treple in 10 yrs. How many times it will becomes after 20 yrs at the same rate of
interest.
(a) 8 times (b) 10 times (c) 9 times (d) 6 times
Solution.
(c) 9 times
Solution
Q2.
If a sum of compound interest becomes three times in 4 years, then with the same interest rate,the sum will become 81 times in.
(a) 10 years (b) 16 years (c) 12 years (d) 18 years
Solution.
(b) 16 years
Solution
Q3.
In how many years a sum of Rs.1000 compounded annually @ 10%, will amount to Rs.1331 ?
(a) 4 (b) 3 (c) 2 (d) 5
Solution.
A = P(1 +
r/100
)
n
1331 = 1000(1 +
10/100
)
n
1331/1000
=
(
11/10
)
n
(
11/10
)
3 =
(
11/10
)
n
n = 3
Solution
Q4.
The compound interest for a certain sum @ 9% p.a. , for first years is Rs.27 . Then what will be the simple interest for the same
money and same interest for 3 years .
(a) 81 (b) 27 (c) 60 (d) 90
Solution.
(a) 81
Note :- For the first year, received interest will be same , for @ simple interest or @ compound interest.
Solution
Q5.
The difference between the simple and compound interest on a certain sum for 3 years at 5% p.a. is Rs.228.75 . Find C.I on the sum for first
year at 5% p.a.
(a) 1640 (b) 1500 (c) 2000 (d) 2010
Solution.
(b) 1500
Difference between S.I and C.I on a certain sum for 3 years =
P(
r/100
)
2
(
300 + r/100
)
Solving this P = 30,000
So, C.I for first year @ 5% is Rs. 1500
Solution
Q6.
The difference between C.I and S.I on a sum of Rs.1000 for 2 years @ r% p.a is Rs. 10, find r .
(a) 16% (b) 10% (c) 20% (d) 15%
Solution.
(b) 10%
Difference between S.I and C.I on a certain sum for 2 years =
P(
r/100
)
2
Solution
Q7.
The difference between C.I and S.I on a certain sum for 2 years @ 10 % p.a. is Rs.20. Find the difference between C.I and S.I on a same
sum for 3 years @ 10% p.a .
(a) Rs. 75 (b) Rs.90 (c) Rs.62 (d) Rs.80
Solution.
Difference between S.I and C.I on a certain sum for 2 years =
P(
r/100
)
2
Difference between S.I and C.I on a certain sum for 3 years =
P(
r/100
)
2
(
300 + r/100
)
P(
r/100
)
2 = 20
= 20 x (
300 + 10/100
)
= 20 x (
310/100
)
= 20 x 3.1 = 62
Solution
Q8.
In how many years, a sum will become double at 5% p.a compound interest.
(a) Approx. 14 years (b) Approx.5 yeara
(c) Approx.16 years (d) Approx. 17 years
Solution.
(a) Approx. 14 years
A = (1 +
r/100
)
n
2P = P(1 +
r/100
)
n
2 = (1.05)
n
Solution
Q9.
A sum of money invested of compound interest doubles itself in four years . It becomes 32 times of itself at the same rate of compound
interest in .
(a) 20 years (b) 22 years (c) 25 years (d) 30 years
Solution.
(a) 20 years
(x1)1/n1 = (x2)1/n2
(2)1/4 = (32)1/x2
(2)1/4 = (2)5/n2
1/4 = 5/n2
n2 = 20
Solution
Q10.
A sum of money compounded annually becomes Rs.1140 in two years and Rs.1425 in 3 years . find the rate of interest per annum .
(a) 39% (b) 20% (c) 15% (d) 25%
Solution.
(1 + r/100
)3
/(1 + r/100
)2
=
1425/1140
1 +
r/100
= 1.25
r/100
= 0.25
r = 25%
Solution
