Simple Interest
6.
A sum become its double in 10yr. finds the annual rate of simple interest.?
Answer: Option C

Explanation: Here, n = 2, T = 10 yr
R = 100 (n- 1)/ T
= 100 (2 – 1) / 10 = 100 / 10 = 10%

7.
A simple interest a sum become 3 times in 20 yr. find the time in which the sum will be double at the same rate of interest ?
A.
8 yr B.
10 yr C.
12 yr D.
14 yr

Answer: Option B

Explanation: Here, n = 3, m= 2, T1 = 20 yr
T2 = m – 1 / m – 1 x T1 = 2 – 1 / 3 – 1 x 20 = 10 yr

8.
A certain sum become 3 fold at 4% annual rate intereset. At what rate, it will become 6 fold ?
Answer: Option A

Explanation: Here, n = 3, m = 6, R1 = 4%
R2 = m = - 1 / n – 1 x R1
= 6 – 1 / 3 – 1 x 4 = 5/ 2 x 4 = 10%

9.
At a simple interest a sum amount to Rs 1012 in 2 1/2 yr and becomes Rs 1067.20 in 4 yr .what is the rate of interest?
A.
2.5% B.
3% C.
6 yr D.
9 yr

Answer: Option C

Explanation: Let age of Ruchi’s = x
Her father’s age = (38 + x)
And her mother age
= (36 + (x- 4)) = (32 + x)
Required differences
= (38 + x) – (32 + x) = 6 yr

10.
A sum was lent out for a certain time. The sum amount to RS 400 at 10% annual interest rate. When the sum was lent out at 4% annual interest rate, it amount to Rs 200. Find the sum ?
A.
Rs 200 / 3 B.
Rs 100 C.
Rs 400 / 3 D.
Rs 500 / 3

Answer: Option D

Explanation: Give R1 = 10%, R2 = 4%
A1 = Rs 400, A2 = Rs 200
According to the formula
P = A2 R1 – A1R2 / R1 – R2
= 200 x 10 - 400 x 4 / 10 – 4
= 200 – 1600 / 6 = 400 / 6 = Rs 200 / 3

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