 # S.I. & C.I. (21)

1. A sum of Rs. 1600 gives a simple interest of Rs. 252 in 2 years and 3 months. The rate of interest per annum is:?
1. 51/2%
2. 8%
3. 7%
4. 6%
5. None of these

Explanation :-

P = 1600 ,    R = ?    SI = 252
T = 2+(3/12) = 2+(1/4) = 9/4 years
R = (SI*100) / (1600/(9/4))
R = 7%

2. A sum of Rs. 1750 is divided into two parts such that the interests on the first part at 8% simple interest per annum and that on the other part of 6% simple interest per annum are equal. The interest on each part (In rupees) is ?
1. 60
2. 65
3. 70
4. 40
5. None of these

Explanation :-

Let the first Part be x, Therefore 2nd part = (1750 -x)
x*8/100 = (1750 – x)* 6/100
8x + 6x = 1750*6
14x = 1750*6
x= Rs. 750
SI = 8% of 750 =Rs. 60

3. Rs. 500 was invested at 12% per annum simple interest and a certain sum of money invested at 10% per annum simple interest at. If the sum of the interests on both the sums after 4 years is Rs. 480, the latter sum of money is?
1. Rs. 450
2. Rs. 750
3. Rs. 600
4. Rs. 550
5. None of these

Explanation :-

SI1 (on 500 at 12% p.a. in 4 years) = (500*12*4)/100 = Rs. 240
Let other sum of money be Rs. x
Total SI = SI1 + SI2
480 = 240 -SI2
SI2 = Rs.240
SI2 = (PRT/100)
240 = (x*10*4)/100
x = Rs. 600

4. A sum of money lent out at simple interest amounts of Rs. 720 after 2 years and to Rs. 1020 after a further period of 5 years. The sum is?
1. Rs. 500
2. Rs. 600
3. Rs. 700
4. Rs. 710
5. None of these

Explanation :-

SI (for 5 years) = Amount after 2 years + Amount after 7 years
SI (for 5 years) = 1020 – 720 = 300
SI (for 2 years) = (300/5)*2 = 120
P = 720 – 120 = Rs.  600

5. In what time will Rs. 72 become Rs. 81 at 25/4% per annum simple interest?
1. 2 years
2. 3 years
3. 2 years 6 months
4. Can’t determine
5. None of these