Aptitude - Compound Interest - Discussion

Discussion Forum : Compound Interest - General Questions (Q.No. 3)
3.
There is 60% increase in an amount in 6 years at simple interest. What will be the compound interest of Rs. 12,000 after 3 years at the same rate?
Rs. 2160
Rs. 3120
Rs. 3972
Rs. 6240
None of these
Answer: Option
Explanation:

Let P = Rs. 100. Then, S.I. Rs. 60 and T = 6 years.

R = 100 x 60 = 10% p.a.
100 x 6

Now, P = Rs. 12000. T = 3 years and R = 10% p.a.

C.I.
= Rs. 12000 x 1 + 10 3 - 1
100
= Rs. 12000 x 331
1000
= 3972.

Discussion:
94 comments Page 9 of 10.

Keerthi said:   4 years ago
1200*{(1+10/100)^3 - 1}, and next step how will become?

Especially- (1200*331/1000).

Please explain to me.
(3)

Harshit said:   4 years ago
How to solve (1 + 10/100) ^3?

Please explain it.
(2)

Vishwanath said:   3 years ago
@Harshit.

First solve brackets, then multiply them into 3 times.

Then, You will get 1331/1000.
(4)

Vishwanath said:   3 years ago
@Keerti.

12000 * 331/1000 = 12 * 331/1 = 3972.
(5)

Kal el said:   3 years ago
There is a difference between 'increase to' and 'increase by'.

So, please describe it clearly to understand.
(4)

Vattikuti shivaram said:   2 years ago
We can solve in a simple way also if we have 12000 as the principal amount then we can.
Divide with a 10% rate
By dividing 12000. With we get 1200 in three times because of three years of interest as SI;
And now doing 1200 we get 3 times 120 for three years CI
We know that ci is recursive with year one 120 divided by 1/10
Then we get 12;
Now 3*1200+3*120+12 = 3972.
(14)

Jay said:   2 years ago
From Where this -1 came? Please explain to me.
(24)

Nishu said:   2 years ago
@All

Here, -1 came from the formula of compound interest as;

C.I = Amount - Principal.
(17)

Rajdeep saha said:   2 years ago
C.I = {12,000(1+10/100)^3} - 12000.
=3,972 => (answer).
(19)

Gaichalung kamei said:   2 years ago
160% increase..
160/100 = 8/5.
Let's assume 5 is the amount.
60% increase of 5 gives 8. There is a difference of 3 between 5 and 8. The given period is 6 yrs.
So, 6/3 = 2.
Now we can calculate the rate.
P × R × T/100 = 5 × R × 2/100 which gives 10%.

Now compound interest for 3 yrs with the same rate.
(11/10)³= 1331/1000.
The given principle is 12000. We get 12 as a multiplying factor.
now, CI = 331×12 = 3972.
(6)


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