Question Detail
- 10%
- 20%
- 30%
- 40%
Answer: Option B
Explanation:
Let sum be x and rate be r%
then, (x*r*15)/100 = 3x [important to note here is that simple interest will be 3x not 4x, beause 3x+x = 4x]
=> r = 20%
Similar Questions :
1. A financier claims to be lending money at simple interest, But he includes the interest every six months for calculating the principal. If he is charging an interest of 10%, the effective rate of interest becomes.
- 10.25%
- 10%
- 9.25%
- 9%
Answer: Option A
Explanation:
Let the sum is 100.
As financier includes interest every six months., then we will calculate SI for 6 months, then again for six months as below:
SI for first Six Months = (100*10*1)/(100*2) = Rs. 5
Important: now sum will become 100+5 = 105
SI for last Six Months = (105*10*1)/(100*2) = Rs. 5.25
So amount at the end of year will be (100+5+5.25)
=
110.25
Effective rate = 110.25 - 100 = 10.25
2. Reema took a loan of Rs 1200 with simple interest for as many years as the rate of interest. If she paid Rs. 432 as interest at the end of the loan period, what was the rate of interest.
- 5%
- 6%
- 7%
- 8%
Answer: Option B
Explanation:
Let rate = R% then Time = R years.
\begin{aligned}
=> \frac{1200*R*R}{100}=432 \\
=> R^2 = 36 \\
=> R = 6\%
\end{aligned}
3. A sum of money at simple interest amounts to Rs. 2240 in 2 years and to Rs. 2600 in 5 years. What is the principal amount
- 1000
- 1500
- 2000
- 2500
Answer: Option C
Explanation:
SI for 3 year = 2600-2240 = 360
SI for 2 year 360/3 * 2 = 240
principal = 2240 - 240 = 2000
4. What is the present worth of Rs. 132 due in 2 years at 5% simple interest per annum
- 110
- 120
- 130
- 140
Answer: Option B
Explanation:
Let the present worth be Rs.x
Then,S.I.= Rs.(132 - x)
=› (x*5*2/100) = 132 - x
=› 10x = 13200 - 100x
=› 110x = 13200
x= 120
5. At 5% per annum simple interest, Rahul borrowed Rs. 500. What amount will he pay to clear the debt after 4 years
- 750
- 700
- 650
- 600
Answer: Option D
Explanation:
We need to calculate the total amount to be paid by him after 4 years, So it will be Principal + simple interest.
So,
\begin{aligned}
=> 500 + \frac{500*5*4}{100}
=> Rs. 600
\end{aligned}
Read more from - Simple Interest Questions Answers
RD Sharma Solutions Class 8 Mathematics Solutions for Compound Interest Exercise 14.2 in Chapter 14 - Compound Interest
Question 31 Compound Interest Exercise 14.2
Find the rate at which a sum of money will become four times the original amount in 2 years, if the interest is compounded half-yearly.
Answer:
Given details are,
Time = 2 years = 2×2 = 4 half years
Let rate = R % per annum = R/2% half years
Let principal be = P
So, Amount becomes = 4P
By using the formula,
A = P (1 + R/100)^n
4P = P (1 + R/2×100)^4
(1 + R/200)^4 = 4
(1 + R/200) = 41/4
1 + R/200 = 1.4142
R/200 = 1.4142-1
= 0.4142
R = 0.4142 × 200
= 82.84%
∴ Required Rate is 82.84% per annum
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Find the rate at which a sum of money will become four times the original amount in 2 years, if the interest is compounded half yearly.
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Solution
Let Principal (P) = Rs. 100
then Amount (A) = Rs. 400
Period (n) = 2 years or 4 half years.
Let R be the rate
% half-yearly, then
AP=(1+R100)n⇒400100=(1+R100)4
⇒(1+R100)4=41
⇒[(1+R100)2]2=(2)2
⇒(1+R100)2=2⇒(1+R100)=√2
⇒1+R100=1.4142
⇒R100=1.4142−1.0000
⇒R100=0.4142⇒R=0.4142×100
⇒R=41.42
∴ Rate
%=41.42% half yearly and
82.84% p.a.
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