Question Detail

Find the rate at Simple interest, at which a sum becomes four times of itself in 15 years.

Answer: Option B

Explanation:

Let sum be x and rate be r%
then, (x*r*15)/100 = 3x [important to note here is that simple interest will be 3x not 4x, beause 3x+x = 4x]

=> r = 20%

1. At 5% per annum simple interest, Rahul borrowed Rs. 500. What amount will he pay to clear the debt after 4 years

Answer: Option D

Explanation:

We need to calculate the total amount to be paid by him after 4 years, So it will be Principal + simple interest.

So,
\begin{aligned}
=> 500 + \frac{500*5*4}{100}
=> Rs. 600
\end{aligned}

2. Find the simple interest on Rs 7000 at 50/3 % for 9 months

Rs. 1075
Rs. 975
Rs. 875
Rs. 775

Answer: Option C

Explanation:

\begin{aligned}
\text{ S.I. = } \frac{P \times R \times T}{100}
\end{aligned}
So, by putting the values in the above formula, our result will be.
\begin{aligned}
\text{ Required result = } \frac{7000 \times 50 \times 9}{3 \times 12 \times 100} = 875
\end{aligned}

[Please note that we have divided by 12 as we converted 9 months in a year format]

3. In how many years Rs 150 will produce the same interest at 8% as Rs. 800 produce in 3 years at 9/2%

Answer: Option B

Explanation:

Clue:
Firstly we need to calculate the SI with prinical 800,Time 3 years and Rate 9/2%, it will be Rs. 108

Then we can get the Time as

Time = (100*108)/(150*8) = 9

4. Rs. 800 becomes Rs. 956 in 3 years at a certain rate of simple interest. If the rate of interest is increased by 4%, what amount will Rs. 800 become in 3 years.

Rs 1052
Rs 1152
Rs 1252
Rs 1352

Answer: Option A

Explanation:

S.I. = 956 - 800 = Rs 156

\begin{aligned}
R = \frac{156*100}{800*3} \\
R = 6\frac{1}{2}\% \\

\text{ New Rate = }6\frac{1}{2}+4 \\
= \frac{21}{2} \% \\

\text{ New S.I. = }800\times\frac{21}{2}\times{3}{100} \\
= 252
\end{aligned}

Now amount will be 800 + 252 = 1052

5. At what rate percent per annum will the simple interest on a sum of money be 2/5 of the amount in 10 years

Answer: Option D

Explanation:

Let sum = x
Time = 10 years.
S.I = 2x /5, [as per question]
Rate =( (100 * 2x) / (x*5*10))%
=> Rate = 4%