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 5 of 18.

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.

Farru_faiz said:   6 years ago
P = sum.
SI = simple interest.

P+SI=815 ; P + SI=854
SI=815-P ; SI=854-P

SI=P*T*R/100
(815-P) =P*3*R/100 ------>1
(854-P) =P*4*R/100 ------>2

---- >>(1/2)

(815-p)/3 = (854-P)/4

(815-P)*4=3*(854-p)
3260-4P = 2562-3P
3260-2562 = 4 P-3P
698=P.
(1)

Manisha Pal said:   6 years ago
We know,

Amount = Principe + interest.
4 year amount= principle + 4 year interest.
3 year amount = principle + 3 year interest.

Then,
39 = 1 year Interest.
Now to calculate principle or sum.
We have formula that, amount - interest.

4 year amount- 4-year interest
854-4*39 =698.

or 3 year amount - 3-year interest.
815-3*39=698.
(1)

Madhav said:   6 years ago
@All.

Amount = Principe + interest.
4 year amount= principle + 4 year interest.
3 year amount = principle + 3 year interest.

Then
39= 1 year Interest
Now to calculate principle or sum
We have formulae that, amount - interest.
4 year amount- 4-year interest
854-4*39 =698.
or 3 year amount - 3-year interest.
815-3*39=698.

Arti said:   6 years ago
S.I For 3rd yr=815.
S.I For 4th yr=815.

Difference for 1yr = 39.
S.I for 3yrs = 39 * 3 = 117
P=815-117 = 698.

Similarly;
S.I for 4yrs = 39 * 4 = 156,
P = 854-156 = 698.

I hope it gets clear to you all.

Tejanth said:   6 years ago
Nice explanation @Gayatri.

Yash said:   6 years ago
A sum of money at simple interest amounts to Rs. 815 in 3 years := P + SI(3 years) = 815
and to Rs. 854 in 4 years := P + SI(4 years) = 854.

p+(p*r*3)/100=815 ------> 1
p+(p*r*4)/100=854 -------> 2
on solving 1 and 2 you get := pr=3900.
put value of pr in eq-1 ,you get := p=698 (answer).
(2)

Nithya said:   6 years ago
Thanks @Gayathri.

Suyash sonawane said:   7 years ago
3 year - 815,
4 year - 854,
4 yr - 3 yr= 854-815,
1 yr=39,
39*3=117,
Sum= 815-117= 698.
(1)

Prabhukiran said:   7 years ago
Nice Explanation, thanks @Vikram.


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