Aptitude - Simple Interest - Discussion

Discussion Forum : Simple Interest - General Questions (Q.No. 7)
7.
An automobile 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%
10.25%
10.5%
None of these
Answer: Option
Explanation:

Let the sum be Rs. 100. Then,

S.I. for first 6 months = Rs. 100 x 10 x 1 = Rs. 5
100 x 2

S.I. for last 6 months = Rs. 105 x 10 x 1 = Rs. 5.25
100 x 2

So, amount at the end of 1 year = Rs. (100 + 5 + 5.25) = Rs. 110.25

Effective rate = (110.25 - 100) = 10.25%

Discussion:
118 comments Page 9 of 12.

Aditya said:   7 years ago
100*r*1/100=10.25 since p*r*t/100= S.I
By, solving we will get r = 10.25 answer.

Arun said:   7 years ago
Why they are assuming p as 100 why can't we take any oter values?

Vikul Chauhan said:   7 years ago
The easiest way to do this question is;

Let principal =100.
A=100 [1+4/100] =112.4864.
The interest of one year 12.48.
Effective rate of interest = 12.5%.

Akash said:   7 years ago
Please tell me, why calculating compound interest for the second half, (since compound interest is interest on interest).

I think the formula should be pr (2T)/100 because we take interest twice a year.

Bijata said:   7 years ago
The effective rate of interest = [1+I/2]^2 -1,
= [1+0.10/2]^2-1,
= [1.05]^2-1,
= 1.1025 - 1,
= 0.1025*100.
= 10.25%.
Note: ^2= it is said for only six month.

Kalpesh sahu said:   7 years ago
eff. interest = ( (1 + r%/(100*t) ) ^ t - 1 )* 100.
r% = rate of interest (10).
t = time divided (in this case = 2).

Soln; ( (1 + 10/(100*2) ) ^ 2 - 1 )* 100,
= ( (1 + 10/200 ) ^ 2 - 1 )* 100,
= ( (1 + 0.05 ) ^ 2 - 1 )* 100,
= ( (1.05)^2 - 1 )*100.
= ( 1.1025 - 1 )*100.
= ( 0.1025)*100,
= 10.25%.

Jhansi said:   6 years ago
@Kalpesh.

What is eff.interest?

RK Hasan said:   6 years ago
it is compound interest actually,

Amount(A) = P(1+10/(2*100))^(2*1) = P(1.1025).
Interest = nr = r = A-P = 0.1025 = 10.25%.

Aashik said:   6 years ago
Why we should take P as only Rs100.

Nadeem said:   5 years ago
Even if we take P different, say 200, answer is the same,
SI (first 6 month ) = 10,
SI( second 6 month) = 10.5,
Then Rate = 20.5/200 * 100 = 10.25.


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