5 Most Important Simple Interest (SI) Questions Concepts with Short Tricks for SSC & Railway Exams

5 Most Important Question Concepts with Short Tricks on Simple Interest For SSC Exams 2023

Question 1:  A sum of Rs 10,000 is lent partly at 8% and remaining at 10% per annum. If the average yearly rate of interest is 9.2%, the two parts are

(1)     Rs 4,000,Rs 6,000

(2)     Rs 4,500, Rs 5,500

(3)     Rs 5,000, Rs 5,000

(4)     Rs 5,500, Rs 4,500

Solution:

Let Rs.  x is lent at 8%

Then, Rs (10000 – x) is lent at for 10% Accordingly,

Other Method:

Hence,

Question 2: A part of Rs 1500 was lent at 10% per annum and the rest at 7% per annum simple interest. The total interest earned in three years was Rs 396. The sum lent at 10% was

(1)    Rs 900

(2)     Rs 800

(3)     Rs 700

(4)     Rs 600

Solution with Short Trick:

S.I. for 3 yrs. = Rs 396

Question 3: A sum of money, at simple interest, triples itself in 15 years. It will become 5 times of itself in

(1)     40 years

(2)     36 years

(3)     30 years

(4)     25 years

Solution:

A = 3P

S.I. = A – P = 2P

Other Method: 

Question 4: A person invests money in three different schemes for 6 years, 10 years and 12 years at 10%, 12% and 15 simple interest respectively. At the completion of each scheme, he gets the same interest. The ratio of his investments is

(1)     6 : 3 : 2

(2)     2 : 3 : 4

(3)     3 : 4 : 6

(4)     3 : 4 : 2

Solution: 

We known,

From Problem (S.I.)₁ = (S.I.)₂ = (S.I.)₃

Question 5: The rate of interest on a sum of money is 4% per annum for the first 2 years, 6% per annum for the next 4 years and 8% per annum for the period beyond 6 years. If the simple interest accrued by the sum for a total period of 9 years is ` 1120, what is the sum?

(1)     Rs 2000

(2)     Rs 2200

(3)     Rs 2400

(4)     Rs 2500

Solution: 

S.I. at the rate of 4% for 2 yr.

S.I. at the rate of 6% for next 4 yr.

For next 3 yr.

Other Method:

Required sum = (1120 x 100)/(2 x 4 + 4 x 6 +3 x 8) = 2000

Solve this

Miscellaneous Simple Interest Question Examples for SSC and Railway Exams

Ex.1: What sum of money will produce Rs.143 interest in   years at  p.c. simple interest?

Solution:

Let the required sum be Rs. P. Then

Rs P = 

To find rate %:-

Since I =                              

Ex.2. A sum of Rs.468.75 was lent out at simple interest and at the end of 1 year 8 months the total amount was Rs500. Find the rate of interest per cent annum.

Solution:

Here, P =Rs468.75, t =  or 

I = Rs.(500-468.75) = Rs.31.25

rate p.c. = 

To find Time:-

Since, I = P t r / 100   

Ex.3: In what time will Rs.8500 amount to Rs.15767.50 at  per cent per annum?

Solution:

Here , interest = Rs.15767.50 – Rs.8500 =Rs.7267.50

Ex.4: The simple interest on a sum of money is 1/9^th of the principal, and the number of years is equal to the rate per cent per annum. Find the rate per cent.

Solution:

Let principal = P, time = t year, rate = t

Then,                         

Hence, rate =  %

Direct formula:

Rate = time =  %

Ex.5: The rate of interest for the first 2 yrs is 3% per annum, for the next 3 years is 8% per annum and for the period beyond 5 years 10% per annum.To fetch interest of 1520 in six years, money did he deposit?

Solution:

Let his deposit be = Rs 100

Interest for first 2 yrs = Rs 6

Interest for next 3 yrs = Rs 24

Interest for the last year = Rs 10

Total interest = Rs 40

When interest is Rs 40, deposited amount is Rs 100

when interest is Rs 1520, deposited amount =  = Rs 3800

Direct formula:

Principle = Interest*100/r₁t₁+r₂t₂+r₃t₃… =  =Rs 3800

Ex.6: A sum of money doubles itself in 10 years at simple interest. What is the rate of interest?

Solution:

Let the sum be Rs 100

After 10 years it becomes Rs 200

Interest = 200 - 100 = 100

Then, rate =  = 

Direct formula:

Time × Rate = 100 (Multiple number of principal – 1)

Or, Rate = 

Using the above formula rate = 

Ex.7: A sum was put at a certain rate for 2 yrs. Had it been put at 3% higher rate, it would have fetched Rs 300 more. Find the sum.

Solution:

Let the sum be Rs x and the original rate be y% per annum. Then, new rate = (y+3) % per annum

xy +3x – xy =15,000 or, x =5000

Thus, the sum =Rs 5000

Shortcut Method : Direct Formula

Sum =  = 

Ex.8. The simple interest on a certain sum of money at 4% per annum for 4 yrs is Rs 80 more than the interest on the same sum for 3 yrs at 5% per annum. Find the sum.

Solution:

Let the sum be Rs.x , then, at 4% rate for 4 yrs the simple interest =  = Rs.  

At 5% rate for 3 yrs the simple interest =  = Rs 

Now, we have,   or, 

Or,  x= Rs 8000

Shortcut Method: For this type of question

Sum =  = Rs 8000

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