Aptitude - Compound Interest - Discussion

Discussion Forum : Compound Interest - General Questions (Q.No. 2)
2.
The difference between simple and compound interests compounded annually on a certain sum of money for 2 years at 4% per annum is Re. 1. The sum (in Rs.) is:
625
630
640
650
Answer: Option
Explanation:

Let the sum be Rs. x. Then,

C.I. = x 1 + 4 2 - x = 676 x - x = 51 x.
100 625 625

S.I. = x x 4 x 2 = 2x .
100 25

51x - 2x = 1
625 25

x = 625.

Discussion:
149 comments Page 7 of 15.

Hiten said:   8 years ago
Diff = pri*(r/100)sqr.
1 = x*(4/100)sqr,
1 = x*(1/25)sqr,
1 = x/625,
x=625.

ADITYA VERMA said:   8 years ago
Short trick of this sum.

If the sum says diff. Of 2 years then apply::
P*R*R/100*100.

If the sum says diff. For 3 years then apply::
P*R*R (300+R)/100*100*100.

Chandan said:   8 years ago
Here, sum= (difference * 10000)/rate squre.

Remya said:   8 years ago
Anu deposit some money in a bank. After 6 years he got 6500rs, then after 2 years, she got 7800 rs. The how much amount will she get after 10 years?

Can anyone solve this?

Yashika said:   8 years ago
The SI = CI when the principal and rate are the same and time is ________.

Please give me the answer.

Prasad Mandati said:   8 years ago
Note:

If,
P= Principal sum x= R/100.
Now,
The difference between Compound and simple interests when compounded annually for two years is Px^2.

Similarly if the same is done for 3 years the difference would be P(x^3 + 3x^2).

Hope it helps you!

Nilesh said:   9 years ago
How 51/625 comes? Please explain that.

Shivesh said:   9 years ago
Derivation of this formula.

Principal x (r%/100)^2 = Difference between interests.

KarthicK said:   9 years ago
@Sudharsan.

Clear explanation Thanks.

MALINIMADHAVAN said:   9 years ago
S.I = PNR/100.
=(PX2X4)/100,
=(PX2X1)/25.

THEREFORE S.I = PX2/25 = 0.008P,
C.I = P(1+R/100)^N -P,
= P(1+4/100)^2 -P,
=P(1+1/25)^2 - P,
= P(25+1/25)^2 -P,
= P(26/25)^2-P,
= P(1.04)^2-P,
= P(1.0816)-P,
=1.0816P-P.
C.I =.0816P.

DIFFERENCE:
CI-SI = 1
0.0816P - 0.08P =1,
0.0016P = 1,
P = 1/0.0016 = 625.
THEREFORE, SUM IN RUPEES IS 625Rs.


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