RRB NTPC - Compound Interest : Aptitude Test (65 Questions with Explanation)

1.

What would be the compound interest accrued on an amount of 6250 Rs. at the end of 2 years at the rate of 12 % per annum? 

   A.) 1570
   B.) 1560
   C.) 1580
   D.) 1590

Answer: Option 'D'

1590

2.

What would be the compound interest accrued on an amount of 2500 Rs. at the end of 2 years at the rate of 10 % per annum?

   A.) 3025
   B.) 3035
   C.) 3125
   D.) 3045

Answer: Option 'A'

Given principal = 2500
No. of years = 2
Rate of interest = 10
Amount = P x (1+r/100)n,
we get Amount = 2500 x (1+10/100)2 Ans : 3025

3.

What would be the compound interest accrued on an amount of 10000 Rs. at the end of 2 years at the rate of 4 % per annum?

   A.) 816
   B.) 10846
   C.) 10816
   D.) 10916

Answer: Option 'A'

Given principal = 10000
No. of years = 2
Rate of interest = 4
Amount = P [ 1 + ( r / 100 )n]
= 10000 x [ 1 +( 4 / 100 )2]
= 10000 x ( 104 / 100 )2
= 10000 x ( 104 / 100 ) x ( 104 / 100 )
= 104 x 104
= 10816
Compound Interest = Amount - Principal

= 10816 - 10000
= 816

4.

Rs. 10000 is borrowed at compound interest at the rate of 4 % annum. What will be the amount to be paid after 2 years?

   A.) 10816
   B.) 10800
   C.) 10808
   D.) 10826

Answer: Option 'A'

Principal : P = 10000 Rs.
Rate of Interest : r = 4 %
Number of years : n = 2
Amount = P x (1 + r/100)n
Amount = 10000 x (1+4/100)2
=10000 x (1+1/25)2
=10000 x (26/25) x (26/25) =10816

5.

What would be the compound interest accrued on an amount of 2500 Rs. at the end of 2 years at the rate of 10 % per annum?   

   A.) 525
   B.) 575
   C.) 3125
   D.) 3045

Answer: Option 'A'

Given principal = 2500
No. of years = 2
Rate of interest = 10
Amount = P x (1+r/100)n,
=> Amount = 2500 x (1+10/100)2
= 2500 (11/ 10)2
= 2500 (121/ 100)
= 25 × 121
= 3025
So, Compound Amount = 3025
Compound Interest = Compound Amount - Principal

=> C.I = 3025 - 2500
=> C.I = 525 Rs.

6.

What would be the compound interest accrued on an amount of 5000 Rs. at the end of 2 years at the rate of 16 % per annum? 

   A.) 1728
   B.) 6528
   C.) 6728
   D.) ​1628

Answer: Option 'A'

Given 
principal = 5000
No. of years = 2
Rate of interest = 16
Amount = P x (1+r/100)n
we get Amount = 5000 x (1+16/100)2
= 5000 x (116 / 100)2 
= 5000 x (116 / 100 ) x (116 / 100)
= 58 x 116
Amount = 6728
Compound interest = Amount - Principal

= 6728 - 5000
= 1728

7.

The difference between the compound interest and simple interest on a certain sum of money at 5% per annum for 2 years is 45. Then the original sum is? 

   A.) Rs.16000/-
   B.) Rs.15000/-
   C.) Rs.18000/-
   D.) Rs.20000/-

Answer: Option 'C'

For 2 years = (1002D)/R2
= (1002 × 45)/(5 × 5) = (10000 × 45)/25 = Rs.18000/-

8.

John invested an amount of Rs. 20000 for 2 years at compound interest at the rate of 6 % per annum. Find the amount he receives at the end of 2 years.  

   A.) 22472
   B.) 22000
   C.) 22372
   D.) 22120

Answer: Option 'A'

Given
Principal : P = 20000 Rs. Rate of Interest : r = 6 % Number of years : n = 2
Amount = P x (1 + r/100)n 
Amount = 20000 x (1+6/100)2
= 20000 x (1+3/50)2
= 20000 x (53/50) x (53/50)
22472.

9.

Find the simple interest on Rs. 2000 at 7 % per annum for 4 years

   A.)  Rs. 485
   B.)  Rs. 450
   C.)  Rs. 560
   D.)  Rs. 760

Answer: Option 'C'

Given
Principal : 2000
Rate of interest : 7
Number of years : 4
Simple Interest = pnr / 100 
= ( 2000 x 4 x 7 ) / 100
Rs. 560 

10.

What will be compounded interest on a sum of Rs.25,000 after 3 years at the rate of 12 p.c.p.a.?

   A.) Rs.9000.30
   B.) Rs.10123.20
   C.) Rs.9720
   D.) Rs.9820

Answer: Option 'B'

Rs.10123.20

11.

What would be the compound interest accrued on an amount of 6500 Rs. at the end of 2 years at the rate of 15 % per annum ?

   A.) 8596.5
   B.) 8596.25
   C.) 8589.75
   D.) 8589.25

Answer: Option 'A'

Given principal = 6500
No. of years = 2
Rate of interest = 15
Amount = P x (1+r/100)n,
we get Amount = 6500 x (1+15/100)2
Ans : 8596.25

12.

A sum of money is borrowed and paid back in two annual instalments of Rs.882 each allowing 5% compound interest .The sum borrowed was:

   A.) Rs.1640
   B.) Rs.1620
   C.) Rs.1680
   D.) Rs.1700

Answer: Option 'B'

Given
The sum borrowed
Present Worth of Rs.882 due 1 year + Present Worth of Rs.882 due 2 year
=> ( 882 ) / 1 + ( 5 / 100)1 + ( 882) / 1 + ( 5 / 100)1
=> (882 / 105 × 100 )1 + (882 / 105 × 100 )1
=> ( 882 /( 21 / 20 ) + ( 882 / (21 / 20)1
=> ( 882 × 20) / (21) + ( 882 × 20 × 20 / 21 × 21 )
=> 42 × 20 + 42 × 20 × 20 / 21
=> 840 + 2 × 20 × 20
=> 840 + 800
=> 1640
The sum borrowed = Rs.1640

13.

Akarsh left a will of Rs. 16,400 for his two sons whose age are 17 and 18 years.They must get equal amounts when they are 20 years at 5% compound interest. Find the present share of the younger son.

   A.) Rs. 5,000
   B.) Rs. 8,000
   C.) Rs. 7,000
   D.) Rs. 9,000

Answer: Option 'B'

Given, total amount (to be shared by two sons at the age of 20 on Compound interest) = Rs. 16,400
Let the Present share (Principal amount) for 17 year old son = "X"
Then the Present share (Principal amount) for 18 year old son = (16,400 - X)
To attain 20 years of age,
=> 17 year old son takes 3 years (N = 3 years on Compound interest)
=> 18 year old son takes 2 years (N = 2 years on Compound interest)
Given, Rate of interest (R) = 5%
Given that, at the age of 20, two sons get equal amount
=> Compound Amount of 17 year old son = Compound Amount of 18 year old son
W.K.T, Formula for Compound Amount = P [1 + (R/100)]N
=> X (1 + 5/100)3 = (16,400 - X) (1 + 5/100)2
=> X (1 + 5/100) = (16,400 - X)
=> (105/100) X = (16,400 - X)
=> [(105/100) X] + X = 16,400
=> 205 X = 16,400 × 100
=> X = 16,40,000 / 205
=> X = 8,000
Therefore, Present share for 17 year old son = Rs. 8,000

14.

The difference between compound interest and simple interest compounded annually on a certain sum of money for 2 years at 4% p.a. is Re.1 The sum (in Rs) is:

   A.) 625
   B.) 525
   C.) 635
   D.) 685

Answer: Option 'A'

625

15.

John invested an amount of Rs. 20000 for 2 years at compound interest at the rate of 6 % per annum. Find the amount he receives at the end of 2 years. 

   A.) 22120
   B.) 22472
   C.) 22000
   D.) 22372

Answer: Option 'B'

Principal : P = 20000 Rs.
Rate of Interest : r = 6 %
Number of years : n = 2
Amount = P x (1 + r/100)n
= 20000 x (1+6/100)2
= 20000 x (1+3/50)2
= 20000 x (53/50) x (53/50)
= 22472
Thus, Amount that Johnreceives at the end of 2 years = Rs.22472

16.

The difference between the simple interest on a certain sum at the rate of 10% p.a. for 2 years and compound interest which is compounded every 6 months is Rs.124.05 .What is the principal sum? 

   A.) Rs.12,000
   B.) Rs.8000
   C.) Rs.10,000
   D.) Rs.6000

Answer: Option 'B'

Let the sum be P
Compound Interest on P at 10% for 2 years when interest is compounded half-yearly
=P(1+ (R / 2)100) 2T−P= P(1+(10 / 2)100) 2× 2− P
=P(1+120)4−P=P(21 / 20) 4− P
Simple Interest on P at 10% for 2 years
=P × R × T /100
=P×10×2100
= P / 5
Then P[(1+5 / 100)4-1] - P x 10 x 2/100 = 124.05
⇒ P[(21/20)4 - 1 - 1/4] = 124.05
⇒ P[(194481/160000) - (6/5)] = 12405 /100
⇒ P[194481-192000 / 160000] = 12405 /100
⇒ P = [(12405/100) x (160000/2481)]
= 124.05 x 64.490
= 7999.9845
= 8000.

17.

Find the simple interest on Rs. 1300 at 10 % per annum for 5 years

   A.) Rs. 650
   B.) Rs. 550
   C.) Rs. 525
   D.) Rs. 615

Answer: Option 'A'

Given
Principal : 1300
Rate of interest : 10
Number of years : 5
Simple Interest = pnr / 100
Simple Interest = (1300 x 5 x 10) / 100
= 13 x 5 x 10
= 650 
So,Simple Interest = 650

18.

John invested an amount of Rs. 20000 for 2 years at compound interest at the rate of 6 % per annum. Find the amount he receives at the end of 2 years.  

   A.) 22472
   B.) 22000
   C.) 22372
   D.) 22120

Answer: Option 'A'

Given
Principal : P = 20000 Rs.
Rate of Interest : r = 6 %
Number of years : n = 2
Amount = P x (1 + r/100)n
=> Amount = 20000 x (1+6/100)2
= 20000 x (1+3/50)2
= 20000 x (53/50) x (53/50)
22472
Therefore, Amount received by John at the end of two years = Rs. 22472

19.

A person receives a sum of Rs. 420 as interest for investing some amount at 10% p.a compounding annually for 2 years. Find the amount invested at the beginning

   A.) 2050
   B.) 2000
   C.) 2100
   D.) 1900

Answer: Option 'B'

Given compound interest ( C.I ) = Rs.420
Rate of interest ( r ) = 10 %
Number of years ( n ) = 2
To find , amount invested at the beginning i.e principal (P)
Amount = P [ 1 + ( r / 100 ) ]n
Amount = C.I + P

=> Amount = C.I + P
=> P [ 1 + ( r / 100 ) ]n= C.I + P
=> P [ 1 + ( 10 / 100 ) ]2= 420 + P
=> P [ 110 / 100 ]2= 420 + P
=> P [ 11 / 10 ]2= 420 + P
=> P x 121 / 100 = 420 + P
=> ( 121 P / 100 ) - P = 420
=> ( 121 P - 100 P ) / 100 = 420
=> 21 P / 100 = 420
=> P = ( 420 * 100 ) / 21
= 2000 
Amount invested at the beginning, P = 2000 Rs

20.

What would be the compound interest accrued on an amount of 14000 Rs. at the end of 3 years at the rate of 5 % per annum?  

   A.) 2256.75
   B.) 2206.75
   C.) 2236.75
   D.) 2216.75

Answer: Option 'B'

Given
Principal = 14000 No. of years = 3 Rate of interest = 5
Amount = P x (1+r/100)n,
we get Amount = 14000 x (1+5/100)3 = 16206.75
C.I = Amount - Principal 
= 16206.75 - 14000 = 2206.75.


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