# S.I. & C.I. (9)

1. If the simple interest on a certain sum of money for 4 years is one–fifth of the sum, then the rate of interest per annum is
1. 4%
2. 7%
3. 6%
4. 5%

Explanation :-

Let the sum of money be x
Therefore SI = x/5
T = 4 years
R = (SI*100) / (P*T) = ((x/5)*100)/(x*4)
=>5%

2. A certain sum in invested for T years. It amounts to Rs. 400 at 10% per annum. But when invested at 4% per annum, it amounts to Rs. 200. Find the time (T).
1. 45 years
2. 60 years
3. 40 years
4. 50 Years

Explanation :-

Let P be The principal , A as Amount
Therefore ,
Time (T) ={(A1 -A2)/[(A1*R2)-(A2R1)]}*100
=> (400-200)/[(200*10)-(400*5)]*100
=> 20000/400 = 50 Years

3. A sum of money is lent at S.I. for 6 years. If the same amount is paid at 4% higher, Arun would have got Rs. 120 more. Find the principal
1. Rs. 200
2. Rs. 600
3. Rs. 400
4. Rs. 500

Explanation :-

SI at 4% for Principal is Rs.120
Therefore ,
P = (120*100)/(4*6)
P = Rs. 500

4. Mr. Mani invested an amount of Rs. 12000 at the simple interest rate of 10% per annum and another amount at the simple interest rate of 20% per annum. The total interest earned at the end of one year on the total amount invested became 14% per annum. Find the total amount invested.
1. Rs. 25000
2. Rs. 15000
3. Rs. 10000
4. Rs. 20000

Explanation :-

SI(1) = 12000*10*1/100 = 1200
SI(2) = (P*20*1)/100 = P/5
Total SI = 1200 + (P/5)
Therefore ,
1200 + (P/5) is the SI for Rs.(12000 + P) at 14% p.a. for 1 year
1200 + (P/5) = [(12000 + P)*14*1]/100
120000 20P 14*12000+14P
6P 14*12000 − 120000
6P = 48000 P =  Rs. 800
Total amount invested = 12000 + P = 12000 + 8000 = Rs. 20000

5. A lent Rs. 4000 to B for 2 years and Rs. 2000 to C for 4 years on simple interest at the same rate of interest and received Rs. 2200 in all from both of them as interest. The rate of interest per annum is :
1. 14%
2. 15%
3. 12%
4. 13.75%