**RRB NTPC Simple & Compound Interest Questions PDF**

Download RRB NTPC Simple & Compound Interest Questions and Answers PDF. Top 25 RRB NTPC Maths questions based on asked questions in previous exam papers very important for the Railway NTPC exam.

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**Question 1: **Mukesh has 30000 rupees with him. He deposits this amount in two different banks. The first bank offers a simple interest of 12 % per annum and the second bank offers a compound interest of 10 % per annum. How much money (approx) should he invest in the second bank so that at the end of second year he gets same amount from both the banks?

a) 17703.67

b) 16607.14

c) 15983.25

d) 17004.33

**Question 2: **A bank offers a simple interest of 10 % pa. Mohit deposits 20000 rupees in the bank. He then withdraws 5000 rupees every 6 months and keeps it in his mattress. What will be the total amount with him at the end of 2 years?

a) 22500

b) 25000

c) 24000

d) 22750

**Question 3: **Amit invests Rs. 20,000 in two banks. He invested half of the sum in a bank that pays compound interest and half in a bank that pays simple interest. The interest rate in both the banks is 10% p.a. How much interest will he make at the end of 2 years?

a) Rs. 2,000

b) Rs. 2,100

c) Rs. 4,000

d) Rs. 4,100

**Question 4: **Ajay lends a sum of Rs. 1000 to Vijay at a rate of 10% p.a for a period of two years. Situation 1: Compound Interest with repayment in two equal annual installments.

Situation 2: Simple Interest with repayment after two years

In which of the two situations is total amount repaid more and by how much?

a) Amount paid in Situation 2 is more by Rs. 48

b) Amount paid in Situation 1 is more by Rs. 48

c) Amount paid in Situation 2 is more by Rs. 10

d) Amount paid in Situation 1 is more by Rs. 10

**Question 5: **What is the compound interest if an amount of Rs. 2500 is lent for three years at 20% p.a?

a) Rs. 1440

b) Rs. 4320

c) Rs. 1728

d) Rs. 1820

**Question 6: **After the demonetization announcement, Rahul went to a bank to deposit 20 notes of Rs. 500 and 30 notes of Rs. 1000. If the bank offers 12% interest compounded annually, in how many years will the amount become Rs. 50,000

a) 1 year

b) 2 years

c) 3 years

d) 4 years

**Question 7: **A shopkeeper bought 20 litres of kerosene type A at Rs. 30/ litres. He also bought Kerosene type B at Rs. 40/litre. He mixed both the types and sold the mixture at Rs. 45/litre and gained 20%. How much of Kerosene type B did he mix into the solution?

a) 20 litres

b) 40 litres

c) 60litres

d) 80litres

**Question 8: **On what sum of money will the for 3 years at 5% per annum to Rs. 630.50.

a) Rs. 1200

b) Rs. 1261

c) Rs. 4000

d) Rs. 3000

**Question 9: **A sum of money was invested at a certain rate for 2 years. Had it been invested at 3% higher rate of interest, it would have fetched Rs. 450 more. The sum invested was:

a) Rs. 7500

b) Rs. 600

c) Rs. 5000

d) Rs. 4500

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**Question 10: **Find the net profit % if the mark up % is 30% and the discount% is 10%?

a) 13%

b) 21%

c) 15%

d) 17%

**Question 11: **If the interest is compounded annually and the compound interest after 3 years at 10% per annum on a sum is Rs. 331, the principal is

a) Rs. 900

b) Rs. 1000

c) Rs. 1050

d) Rs. 1100

**Question 12: **At what rate of compound interest a sum will be $\frac{25}{16}$ times of itself in 2 years?

a) 16%

b) 18%

c) 20%

d) 25%

**Question 13: **The simple interest on a certain sum at the rate of 4% per annum in 4 years is Rs. 80 more than the simple interest on the same sum at 5% per annum after 3 years. The sum is

a) Rs. 7000

b) Rs. 7,500

c) Rs. 8000

d) Rs. 8,500

**Question 14: **A certain amount of money becomes 4 times after 12 years when kept at a certain rate of simple interest. Find the ratio of the net amount after 2 years to the initial amount if the same principal was compunded annually at the same rate of interest?

a) 1,625

b) 6,25

c) 1.25

d) 1.5625

**Question 15: **Find the difference between the CI and SI for the principal of Rs 10,000 for two years at the rate of 10% per annum if the principal is compounded half yearly.

a) 150

b) 155

c) 145

d) 165

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**Question 16: **One-fourth of an amount was loaned at simple interest with 2% rate of interest and the remaining part was lent on simple interest at 3% rate of interest What is the average rate of interest for the whole amount ?

a) $2\frac{1}{4}\%$

b) $2\frac{3}{4}\%$

c) $1\frac{1}{4}\%$

d) $4\%$

**Question 17: **A certain amount which was loaned on simple interest doubled in 10 years Then the amount received is loaned on compound interest for another 2 years on the same rate What is the total rise in the amount after 12 years with the initial principal amount ?

a) 42%

b) 142%

c) 242%

d) 150%

**Question 18: **The simple interest at the rate of 8% on the amount Rs. 20,000 for 3 months is

a) 400

b) 600

c) 500

d) 200

**Question 19: **What is the interest earned in the second year on a sum of Rs 20,000, compounded annually at 10% p.a.?

a) Rs 2200

b) Rs 2000

c) Rs 2400

d) Rs 1800

**Question 20: **On what sum of money will the compound interest for 3 years at 5% per annum amount to Rs. 630.50 ?

a) Rs. 1200

b) Rs. 1261

c) Rs. 4000

d) Rs. 3000

**Question 21: **One-Sixth of an amount was given on simple interest with the rate of 3% and remaining amount was given on the simple interest rate of 5%. What will be the avg. rate of the whole amount? (Time is same for both the interests)

a) 25/6%

b) 34/5%

c) 27/7%

d) 28/6%

**Question 22: **A certain amount get tripled when given on a simple interest for 20 years. Then the amount received is given on compound interest for 2 years on the same rate. What will be the the total rise after 22 years with the initial principal amount?

a) 363%

b) 263%

c) 163%

d) 178%

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**Question 23: **What is the sum which earns Rs. 420 as compound interest in second year at the annual interest rate of 5% ?

a) Rs. 4,000

b) Rs. 42,000

c) Rs. 8,000

d) Rs. 21,000

**Question 24: **A person invested some money at the rate of 6% simple interest. At the end of three years, he got Rs. 900 as SI. If interest is put at the rate of compound interest annually, how much more interest would he got in three years?

a) Rs. 38.13

b) Rs. 25.33

c) Rs. 55.08

d) Rs. 35.30

e) Other than those given as options

**Question 25: **A person invested certain amount in Scheme A which offers 5% Simple Interest. Had he invested in Scheme B which offers 5% Compound Interest, he would have earned Rs.100 more. Find the sum.

a) Rs.1000

b) Rs.10000

c) Rs.5000

d) Rs.40000

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**Answers & Solutions:**

**1) Answer (B)**

Let us assume that Mukesh deposited x in second bank. So at the end of 2 years it will become 1.21x in bank 2.

Now he must have invested 30000 – x in bank 1.

The interest earned will be (30000 – x)*.12*2 = .24*30000 – .24x = 7200 – .24x

Hence, the amount will be 7200 – .24x + 30000 – x = 37200 – 1.24x

We have been given that 1.21x = 37200 – 1.24x

=> 2.24x = 37200

=> x = 16607.14

Hence, option B is the correct answer.

**2) Answer (A)**

For first 6 months principal will be 20000. For the next 6 months, it will be 15000. For next 6 months, it will be 10000. For last six months it will be 5000.

Thus, the interest earned by him will be

20000*10*.5/100 + 15000*10*.5/100 + 10000*10*.5/100 + 5000*10*.5/100

=> 1000 + 750 + 500 + 250 = 2500

Hence, total amount will be 22500.

**3) Answer (D)**

The principal in the bank with simple interest is Rs. 20,000/2 = Rs. 10,000

Interest earned = 10,000 * 2 * 10% = Rs. 2,000

The principal in the bank with compound interest is Rs. 20,000/2 = Rs. 10,000

Interest earned = $10,000 * 1.1^2$ – 10,000 = Rs. 2,100

Total interest earned = 2,000 + 2,100 = Rs. 4,100

**4) Answer (A)**

Situation 1:

Let the installment amount = x

Amount after 1 year = 1000 + 1000*10% = 1100

Amount for second year after repaying installment = 1100 – x

Amount to be paid after 2 years = (1100 – x) + (1100-x)*10% = 1.1(1100-x)

This should be equal to x. Hence we have

1.1(1100-x) = x => x = 576.20

Hence total amount paid = 576.20 * 2 = 1152.4

Situation 2:

Total interest = 2 * 1000*10% = Rs. 200

Hence Total amount repaid = 1200

Hence the amount paid in situation 2 is more than the amount paid in situation 1 by around Rs. 48.

**5) Answer (D)**

The amount to be returned at the end of three years equals $2500 \times (1+0.2)^3 = 2500 \times 1.728 = 4320$

Therefore the compound interest equals $4320 – 2500 = 1820$

**6) Answer (B)**

Total amount deposited = 20 * 500 + 30 * 1000 = 10,000 + 30,000 = 40,000

So, the amount after 1 year = 40,000 * 1.12 = Rs. 44,800

Amount after 2 years = 44,800 * 1.12 = Rs. 50,180

So, it takes 2 years for the amount to become Rs. 50,000

**7) Answer (C)**

Let x be the litres of kerosene type B bought by the shopkeeper.

1/3 = 20/X

x = 60

So the answer is option C.

**8) Answer (C)**

$ P (1 + .05) ^ {3}$ – P= 630.5

Solving for P, we get P = 4000

**9) Answer (A)**

Let $x$ be the sum of money invested at simple interest and $r$ be the rate of interest.

The interest at the end of 2 years=$P$x$t$x$r/100=2xr$ -(1)

The interest at the end of 2 years if $r$ is increased by 3%=$2x(r+3)$ -(2)

Given (2)-(1)=450

=>$6x=450$

∴$x= 7500$

**10) Answer (D)**

Let the CP = 100

Mark Up = 30%

MP = 130

Disount = 10%

SP = 90% of 130 = 117

Gain% = (117-100)/100 = 0.17 = 17%

**11) Answer (B)**

$ P \times (1 + \frac{10}{100}) ^{3} $= P + 331

1.331P = P + 331

So, P = 1000

**12) Answer (D)**

P * $ (1 + \frac{r}{100})^{2} = P * \frac{25}{16} $

Implies $ (1 + \frac{r}{100})^{2} = \frac{25}{16} $

$ 1 + \frac{r}{100}= \frac{5}{4} $

r = 25%

**13) Answer (C)**

Let the principal be P

SI = P xT x R/100

difference = P x 4 x 4 /100 – P x 5 x 3/100

= 16P/100 – 15P/100 = 80

P = 8000 Rs.

**14) Answer (D)**

Since the money becomes 4 times

3x = x*r*12/100

r = 25% p.a.

Net amount after 2 years = x$(1+r/100)^2$

Net amount after 2 years/x =$1.25^2$ = 1.5625

**15) Answer (B)**

$SI =\frac{P*R*T}{100}$

$SI =\frac{10000*10*2}{100}$

SI = Rs 2000

Amount after 2 years = P$(1+\frac{R}{100n})^{nt}$

n = 12/6 (Since the interest is compounded semi annually) = 2

Amount after 2 years = 10000$(1+\frac{10}{100*2})^{2*2}$ = 12155.0625

CI = 12155.625 – 10000 = Rs 2155.625

CI-SI = Rs(2155.0625-2000) = Rs 155.0625

**16) Answer (B)**

Let the amount be 100 Rs.

One fourth of it is at 2 % pa

So, 25 x 2 x 1 /100 = .5

The rest is on 3% pa interest.

So, 75 x 3 x 1 /100 = 2.25

So total interest = 2.75

Interest rate = ?

Interest rate = i x 100/ pt

= 2.75 x100/100 = 2.75%

**17) Answer (B)**

The amount doubled in 10 years. So, the interest = principle.

So, rt/100 = 1

r = 10% pa

Now compound interest = ?

2P $(1 + .1) ^ {2}$ = 2P x 1.21 = 2.42P

Total rise is P to 2.42P = rise of 142%

**18) Answer (A)**

S.I=P x r x t/100 , t in years

=(20,000 x 8 x 3)/( 100 x 12)=400

**19) Answer (A)**

Interest earned in the first year = 20000 * 1 * 10/100 = Rs 2000

Principal for the second year = Rs 20,000 + Rs 2,000 = Rs 22,000

So, interest for the second year = 22000 * 1 * 10/100 = Rs 2200

**20) Answer (C)**

$ P (1 + .05) ^ {3}$ – P= 630.5

Solving for P, we get P = 4000

**21) Answer (D)**

Let’s say amount is x and rate is r% for t time

So Total simple interest will be = \frac{xrt}{100} = \frac{3xt}{600} + \frac{25xt}{600}

Hence, r = $\frac{28}{6} \% $

**22) Answer (B)**

Let’s say initial amount = x

after simple interest = 3x

Simple interest = 2x = x*($\frac{r}{100}$)*(20)

So r = 10%

Now after giving the amount on compound interest, amount will be = $3x(1+10\%)^{2} = 3.63x$

Increment from the initial principal amount = 2.63x i.e 263%

**23) Answer (C)**

x * 1.05 * 1.05 – x * 1.05 = 420

implies x = 8000 Rs.

**24) Answer (C)**

S.I=900=6/100 x 3 x P

=>P=5000

C.I amount=A=P(1 + r/100)$^{t}$=5000(1 + .06)${3}$

=5955.08

=>C.I=955.08

∴ the person would get Rs 55.08 additionally.

**25) Answer (B)**

Let the principal be Rs.10000

Simple Interest at 5% SI for 2 years = $\dfrac{10000\times5\times2}{100} = Rs.1000

Amount for 1 year at 5% CI = 105% of Rs.10000 = Rs.10500

Amount for 2 years at 5% CI = 105% of Rs.10500 = Rs.11025

Total Compound Interest = Rs.11025 – Rs.10000 = Rs.1025

Difference between SI and CI = Rs.1025 – Rs.1000 = Rs.25

Given that the difference = Rs.100

Rs.25 → Rs.100

Rs.10000 → ?

= $\dfrac{10000\times100}{25} = Rs.40000$

Hence, Principal = Rs.40000

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