# Simple interest

11.

A sum of money amounts to Rs. 9800 after 5 years and Rs. 12005 after 8 years at the same rate of simple interest. The rate of interest per annum is:
A.     5%    B.     8%
C.     12%    D.     15%

Explanation:

S.I. for 3 years = Rs. (12005 – 9800) = Rs. 2205.

S.I. for 5 years = Rs.         2205     x 5         = Rs. 3675
3

Principal = Rs. (9800 – 3675) = Rs. 6125.

Hence, rate =         100 x 3675     %     = 12%
6125 x 5

12.

What will be the ratio of simple interest earned by certain amount at the same rate of interest for 6 years and that for 9 years?
A.     1 : 3    B.     1 : 4
C.     2 : 3    D.     Data inadequate
E.     None of these

Explanation:

Let the principal be P and rate of interest be R%.

Required ratio =
P x R x 6
100
=     6PR     =     6     = 2 : 3.
P x R x 9
100
9PR     9

13.

A certain amount earns simple interest of Rs. 1750 after 7 years. Had the interest been 2% more, how much more interest would it have earned?
A.     Rs. 35    B.     Rs. 245
C.     Rs. 350    D.     Cannot be determined
E.     None of these

Explanation:

We need to know the S.I., principal and time to find the rate.

Since the principal is not given, so data is inadequate.

14.

A person borrows Rs. 5000 for 2 years at 4% p.a. simple interest. He immediately lends it to another person at 6 p.a for 2 years. Find his gain in the transaction per year.
A.     Rs. 112.50    B.     Rs. 125
C.     Rs. 150    D.     Rs. 167.50