Question

1-. On what sum of money lent out at 9% per annum simple interest for 6 years does the simple interest amount to 810 .

2 -. At what rate of interest per annum will a sum double itself in 8 years .

3-. In how many years will rupee 870 amount to rupee 1044 the rate of interest being 5% .

4-. A and B together can do a job in 12 days. B alone can finish it in 28 days . In how many days can A alone finish the work.

5-. Radha can do a job in 20 days . How much work will be finished in 12 days.​

Answer 1

Answers:

1 - Let the sum be P.

Amount = Rs.810

Simple Interest = Rs.810

Rate = 9% per annum

Time = 6 years

S.I = P × R × T/100

810 = P × 9 × 6/100

81000 = 54P

P = 1500

Hence, the sum is Rs.1500

2 - Let the sum be P.

Amount = 2P

Simple Interest = P

Time = 8 years

S.I = P × R × T/100

P = P × R × 8/100

R = (100/8)% = 12.5% per annum

3 - Principal = Rs.870

Amount = Rs.1044

Hence, S.I = Rs.(1044 - 870) = Rs.174

Rate = 5% per annum

Let the time period be T.

S.I = P × R × T/100

174 = 870 × 5 × T/100

T = 4 years

4 - A and B can do a work in 12 days. In 1 day A and B can do 1/12th work. B alone can do it in 28 days. In 1 day B can do 1/28th work. Hence, A's 1 day work = 1/12 - 1/28 = 1/21. Therefore, A alone can finish the work in 21 days.

5 - Radha can do a job in 20 days. In 1 day she can do 1/20th work. Hence, work done in 12 days = 1/20 × 12 = 3/5

Answer 2

Simple interest and quantitative aptitude.

Explanation:

Question 1:

Given: Rate, R = 9%, Simple interest, SI = Rs. 810, Time, T = 6 years, Principal, P = ?.

Simple interest, SI = $\frac{P * T * R}{100}$

P = $\frac{810 * 100}{6 * 9}$

P = Rs. 1500.

_______________________________________________________

Question 2:

Given: Simple Interest, SI = P, Rate = ?, Principal = P, T = 8 years.

Simple interest, SI = $\frac{P * T * R}{100}$

R = $\frac{P * 100}{P * 8}$

R = 12.5%

The rate of interest per annum will a sum double itself in 8 years is 12.5%.

Question 3:

Given: Principal = Rs. 870, Amount = Rs. 1044, rate = 5%, Time = ?

We know that SI = A - P ⇒ 1044 - 870

SI = Rs. 174.

Simple interest, SI = $\frac{P * T * R}{100}$

174 = $\frac{870 * 5 * T}{100}$

T = 5 years.

Question 4:

Given: A + B  can do a job = $\frac{1}{12}$ days

B alone can finish the job = $\frac{1}{28}$ days.

A alone finish the work = ?

Work done by A alone = $\frac{1}{12} - \frac{1}{28}$

= $\frac{28 - 12}{336}$

= $\frac{6}{336}$

= $\frac{1}{21}$

Therefore, A alone can finish the work in 21 days.

To know more:

In how many years will Rs 870 amount to Rs 1044 the rate of interest being 2 1/2 % p.a. ?

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