Question 1

If a certain sum is doubled in 8 yr on simple interest, in how many year will it be four times?

Accepted Answer

Let the sum be Rs 'y' , so amount = 2y Simple interest =Rs y Let R be the rate of interest, R= (100 x SI)/(P x T) = (100 x y) / (y x 8) = 12.5 % where SI= Simple Interest P = Principal T = Time now, the needed amount = Rs 4y since SI = Rs (4x-x)= Rs 3y since T= (100 x SI)/(P x R) = (100 x 3y )/(y x 125)= 24 yr

Question 2

A sum of money at simple interest amount to Rs 1260 in 2 yr and Rs 1350 in 5 yr, then the rate percent per annum is?

Accepted Answer

Simple in 3 year = Rs( 1350 - 1260) = Rs 90 Simple in 2 year = (2/3) &time; 90= Rs 60 Principal = Rs (1260 -60)= Rs 1200 Rate, R= (100 x SI)/(P x T)= (100 x 60)/(1200 x 2)=60/24= 25 % where , SI= Simple Interest P= Principal T= Time

Question 3

The difference of 13% per annum and 12% of a sum in 1 year is Rs 110.Then the sum is?

Accepted Answer

Let the sum be 'y' then, [(y x13 x 1)/100 ]- [( y x 12 x 1) / 100]=110 since ( y / 100 ) = Rs 110 ∴ Y = Rs 11000

Question 4

At what rate percent per annum simple interest , will a sum of money triple itself in 25 year?

Accepted Answer

Let principal amount = P As amount =3P, T=25 yr ∴ SI=3P-P=2P ∴ Rate R = (100 x SI)/(P x T) where, SI= Simple Interest T = Time = (100 x 2P)/(P x 25)=8%

Question 5

A certain sum at simple interest amounts to Rs 1040 in 3 Yr and to Rs 1360 in 7 yr.Then the sum is?

Accepted Answer

Simple Interest for 4 yr = Rs(1360 - 1040 ) = Rs 320 so, Simple Interest for 3 yr= Rs [(320/4) x 3]= Rs 240 Sum = Rs (1040-240)= Rs 800

Question 6

If the rate of simple interest is 12% per annum the amount that would fetch interest of Rs 6000 per annum is?

Accepted Answer

Rate of Interest = 12% per annum Simple Interest =Rs 6000 per annum Let 'P' is the principal SI= (P x R x T)/100 where , SI= Simple Interest T= Time R= Rate ∴ 6000=(P x 1 x 12)/100 ∴ P =(6000 x 100)/12 = Rs 50000 Hence the required amount is Rs 50000

Question 7

The simple interest on a certain sum for 3 years at 14% per annum is Rs. 235.20. The sum is?

Accepted Answer

Required sum = Rs. (100 x SI ) / ( T x R ) = (100 x 235.20) / (3 x 14) = Rs. 560

Question 8

A sum of money amounts to Rs. 702 in 2 years and Rs. 783 in 3 years. The rate percent is?

Accepted Answer

S.I. for 1 year = Rs. (783 - 702) = Rs 81 S.I. for 2 years = Rs. (81 x 2) = Rs. 162 ∴ Sum = Rs. (702 - 162) = Rs. 540 ∴ Required rate = = (100 x SI) / (P x T) = (100 x 162) / (540 x 2) % = 15%

Question 9

If Rs. 64 amount to Rs. 83.20 in 2 years. What will Rs. 86 amount to in 4 years at the same rate percent per annum?

Accepted Answer

S.I on Rs. 64 for 2 year = Rs. 19.20 ∴ Rate = (100 x SI) / (P x T) = (100 x 19.20) / (64 x 2) = 15% ∴ S.I On Rs. 86 for 4 year = (P x R x T) / 100 = Rs. (86 x 4 x 15 ) /100 = Rs.51.60 ∴ Amount of Rs. 86 after 4 years = Rs. (86 + 51.60) = Rs. 137.60

Question 10

A sum of money amounts to Rs. 850 in 3 years and Rs. 925 in 4 year. The sum is?

Accepted Answer

S.I for 1 year = Rs. (925 - 850) = Rs. 75 S.I for 3 year = Rs. (75 x 3) = Rs. 225 ∴ Sum = Rs. (850 - 225) = Rs. 625

Question 11

A sum of money put at simple interest trebles itself in 15 years. The rate per cent per annum is?

Accepted Answer

Let principal = P Then, SI = 2P & Time = 15 years ∴ Required rate = (100 x SI) / (P x T) = (100 x 2P) / (P x 15) = 200/15 = 131/3 per annum

Question 12

At the certain rate of simple interest, a certain sum doubles itself in 10 years. It will treble itself in?

Accepted Answer

Let principal = P. Then, S. I = P. and Time = 10 years ∴ Required time = [(n - 1) x t] / (m - 1) = [(3 - 1) x 10] / (2 - 1) = 20 years

Question 13

A sum of money at simple interest amounts to Rs. 2240 in 2 years and Rs. 2600 in 5 years. The sum is?

Accepted Answer

S.I for 3 years = Rs. (2600 - 2240) = Rs . 360 S.I for 2 years = Rs. (360/3 x 2) = Rs. 240 ∴ Required sum = Rs . (2240 - 240) = Rs. 2000

Question 14

The simple interest at R% for R years will be Rs. R on a sum of?

Accepted Answer

Sum = (100 x SI) / (R x T) = (100 x R) / (R x R) = Rs. 100/R

Question 15

At simple interest, a sum doubles after 20 years. The rate of interest per annum is?

Accepted Answer

Let sum = P, then SI = P and Time = 20 years ∴ Required rate = (100 x SI)/(P x T) = (100 x P) / (P x 20) = 5% per annum

Question 16

What annual payment will discharge a debt of Rs. 580 due in 5 years, the rate being 8% per annum?

Accepted Answer

Let the annual installment be Rs. P Then, [P + (P x 4 x 8)/100] + [P + (P x 3 x 8) / 100] + [P + (P x 2 x 8)/100 ] + [ P + (P x 1 x 8)/100] + P = 580 ⇒ 33P/25 + 31P/25 + 29P/25 + 27P/25 + P = 580 ⇒ (120 + 25)P = 580 x 25 ∴ P = 100

Question 17

Ashok took a loan of Rs. 15000 for 3 years at simple interest . If the total interest paid is Rs. 2700. What is the rate of interest per annum?

Accepted Answer

∵ Rate = [(interest x 100) / (Principal x Time) ] % ⇒ Rate = (2700 x 100) / (15000 x 3) % ∴ Rate = 6%

Question 18

Yogesh borrowed Rs. 12000 at simple interest for 5 years, If he paid Rs. 3600 as simple interest after 5 years, What is the rate of interest per cent per annum?

Accepted Answer

Rate = [(interest x 100) / (Principal x Time)] % = (3600 x 100) / (12000 x 5) = 6 %

Question 19

If a sum of money double itself in 20 years. What is the rate of simple interest per cent per year?

Accepted Answer

Let the principal = Rs. P ⇒ Amount = Rs. 2P ⇒ Interest = 2P - P = Rs.P ∴ Rate = (interest x 100) / (Principal x 20) = (P x 100) / (P x 20) = 5%

Question 20

Mr. Patel borrowed Rs. 8000 from Mr. Chobey at simple interest. After 2 years he paid Rs. 800 more than what be borrowed and thus cleared the loan. What was the rate of interest?

Accepted Answer

Rate = (Interest x 100) / (Principal x Time) = (800 x 100) / (8000 x 2) = 5%

Simple Interest Questions