Aptitude - Simple Interest - Discussion

Discussion Forum : Simple Interest - General Questions (Q.No. 1)
1.
A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years. The sum is:
Rs. 650
Rs. 690
Rs. 698
Rs. 700
Answer: Option
Explanation:

S.I. for 1 year = Rs. (854 - 815) = Rs. 39.

S.I. for 3 years = Rs.(39 x 3) = Rs. 117.

Principal = Rs. (815 - 117) = Rs. 698.

Discussion:
171 comments Page 6 of 18.

Suraj.D said:   9 years ago
Please tell me if we subtract 854- 815 we get principal+ s.I for 1 year. Then can we consider it only s.I for 1 year? Please explain me.

Shubham Mude said:   6 years ago
We can also use the below formula:
(A1*T2 - A2*T1) / (T2-T1)
= (815*4 - 854*3) / (4-3)
= (3260 - 2562) / 1
= 698.

Hence, the answer.

Stuti said:   1 decade ago
Hi.

There is a simple shortcut for solving this question.

P/Sum = A1n2-A2n1/n2-n1.

= 815*4-854*3/4-3.

= 3260-2562/1 = 698.

Koishik mandal said:   8 years ago
S.I. for 1 year = Rs. (854 - 815) = Rs. 39.
S.I. for 3 years = Rs.(39 x 3) = Rs. 117.

Principal = Rs. (815 - 117) = Rs. 698.

Hari said:   1 decade ago
I like this type of solutions thank you

I think this answer also

1year 854-815=39

3years 39*4=156

854-156=698

Lelisa said:   7 years ago
4y-3y =1y so that 1y can be Rs. (854-815) Rs.39.

So, 3 years then 39 * 3 = 117.
So the principal is 815-117 =698.

Pradeep said:   9 years ago
Let 1 yr int .....x.
3yr int.......3x.
4yr int........4x.
(P+4x) - (P+3x) = 854 - 815,
x = 39.

Mahesh Narayankar said:   5 years ago
Let x=principal interest.
x+3*SI = 815.
x+4*Si = 854.

SI for 1 Year=854-815=39,
x+3*39=815,
x=815-117=698.
(1)

Sase m said:   8 years ago
Why should we apply like this;

s.i for 1 year = Rs 854-815=39
1yr = 39 then 4y = 156
then 854-156=698.

Naren said:   10 years ago
815-p = 3*x.1 -----> equation 1.

854-p = 4*x.2 -----> equation 2.

Divide equation 1 with equation 2.


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