Aptitude - Simple Interest - Discussion

S.I=725*r*2/3*100+362.50*2r+1/3*100=33.50.

Therefore,
1450R/300+750R/300=33.50,
= 4.83R+2.5R=33.50,
= 7.33R=33.50,
= R=33.50/7.33,
= R=4.5.

I think correct answer is 2.77...725 is only for 8 months/for the next four month a total of 725 + 362.5 is under consideration.

Let me clear,

Rs 725 is not taken back. It is uniform through out the year.

Second thing --->
The rate of interest which is twice in case of 362.50.
Not for (725+ 362.50).

That's why it has taken twice rate of interest for 362.50.

The sum 725 rs has certain interest rate R for 1 year not for 8 months, 8months is just a hint for the next part of the question (12-8=4). They could have simply said for the last 4 months the interest is twice the initial rate for an EXTRA SUM 362.5 rs.

In the question, he gives extra 362.5 sum at the 8th month for twice of R, which does not mean initial sum of 725 Rs it's interest rate is only for 8 months or should be calculated for 8 months.

1st principal should be calculated for 8 months, not for one year.

Here, the original rate is for 1 year(s); the new rate is for only 4 months i.e. year(s). Please explain this.

@Rajni.

I thank you for raising the question.

Look here, any interest is calculated, as we generally know at the end of the year. Now you read the problem carefully. The first loan is taken at the beginning of the year, thus the person will be charged the interest for 12 months, but the last one is after 8 months, meaning the person will be charged only 4 months, he has no relation with the previous 8 months, thus here 4 months is our considering fact and you know very well 4 months = 4/12year=1/3year. Thus it's included 1/3year.

In the question, it's mentioned the interest is per annum hence we need to take T as 2/3 in first case & 1/3 in the second case.

How, 2175 has come?

There are 2 loan consider A(725) and B(362.50). Loan A is taken for 1 year with some interest (R), at the end of eight-month another loan is taken which is B with interest (2R). That is one loan is for 1 year and another loan is for 4 months. By the end of the year SI = loan for one year(725) + loan for 4 months(362.5) ie 725 x R x 1 /100+ 362.50 x 2R x 1/100 * 3 = 33.50.