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?
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. |
|
|||||||||||||
|
||||||||||||||
| = 3972. |
Discussion:
94 comments Page 2 of 10.
Ganesh said:
7 years ago
@All.
1st find rate R of 6 yr Assume 100rs, for 6 yr.
R=(100 * s.i/p * n) = 10%.
After that find C.I using ratio proposition of 3 yr is 3:3:1 is fixed and 2yr is (2:1).
Then 1st yr c.i. is 3* 10% of 12000,
2nd yr C.I is 3* 10% of 1200,
3rd yr C.I is 1* 10% of 120 add all the yrs.
3600 + 360 + 12 = 3972 is the answer.
1st find rate R of 6 yr Assume 100rs, for 6 yr.
R=(100 * s.i/p * n) = 10%.
After that find C.I using ratio proposition of 3 yr is 3:3:1 is fixed and 2yr is (2:1).
Then 1st yr c.i. is 3* 10% of 12000,
2nd yr C.I is 3* 10% of 1200,
3rd yr C.I is 1* 10% of 120 add all the yrs.
3600 + 360 + 12 = 3972 is the answer.
(1)
Vani said:
10 years ago
Suppose principle is 100.
Then simple interest becomes 60.
Then rate will become 10% by using the formula,
(ptr)/100 = simple interest.
Now the compound interest in 3 years with the rate 10% is,
10+10+1(interest on interest)+11+1.1 = 33.1.
12000 --- 100
?----------- 33.1
The answer is 3972.
Then simple interest becomes 60.
Then rate will become 10% by using the formula,
(ptr)/100 = simple interest.
Now the compound interest in 3 years with the rate 10% is,
10+10+1(interest on interest)+11+1.1 = 33.1.
12000 --- 100
?----------- 33.1
The answer is 3972.
Amit said:
1 decade ago
@Kusum
Simple interest formula
SI = PRN / 100
So, SI * 100 = PRN which derives new formula for R as
R = (SI * 100) / PN
Let P = Rs. 100. Then, S.I. Rs. 60 and T = 6 years.
Put all this into simple interest formula
R = (100 x 60 ) / 100 x 6 = 10% p.a.
Hope you will get it :)
Simple interest formula
SI = PRN / 100
So, SI * 100 = PRN which derives new formula for R as
R = (SI * 100) / PN
Let P = Rs. 100. Then, S.I. Rs. 60 and T = 6 years.
Put all this into simple interest formula
R = (100 x 60 ) / 100 x 6 = 10% p.a.
Hope you will get it :)
Neha said:
1 decade ago
@dibyajyoti Hazarika.
(1+ 10/100)^3 -1
After L.C.M. it will be
{(100+10)/100}^3 -1
(110/100)^3 -1
(11/10)^3 -1 //(11x11x11=1331)and (10x10x10=1000)
(1331/1000)-1
After L.C.M.
(1331-1000)/1000
331/1000
I think now you understand about 331
(1+ 10/100)^3 -1
After L.C.M. it will be
{(100+10)/100}^3 -1
(110/100)^3 -1
(11/10)^3 -1 //(11x11x11=1331)and (10x10x10=1000)
(1331/1000)-1
After L.C.M.
(1331-1000)/1000
331/1000
I think now you understand about 331
Satya said:
1 decade ago
60% is equal to 60/100 i.e., S.I means adding same rate of interest every year, So here we knew that 60% is increased in 6 years, i.e., Every year it is increased by 10%.
So that 10% * 6 years= 60% for 6 years. So that rate of interest = 10%.
So that 10% * 6 years= 60% for 6 years. So that rate of interest = 10%.
Javeed said:
2 decades ago
Dude here principle is Rs. 12000, so amount = P(1+r/100)^t
C.I = amount - principle i.e., p((1+r/100)^t )-p
Removing 'p' common factor we get:
p((1+(R/100)^T)-1)
HERE 1200 IS REMOVED AS COMMON FACTOR SINCE IT IS THE VALUE OF P.
C.I = amount - principle i.e., p((1+r/100)^t )-p
Removing 'p' common factor we get:
p((1+(R/100)^T)-1)
HERE 1200 IS REMOVED AS COMMON FACTOR SINCE IT IS THE VALUE OF P.
Yamini said:
1 decade ago
@Subash
There was no confusion in the given answer, here -1 is nothing but as you said Amount = {P x (1 + (R/100)^N)} - P so from this just take common as P then you get
Amount=[P x {(1 + (R/100)^N)-1}].
There was no confusion in the given answer, here -1 is nothing but as you said Amount = {P x (1 + (R/100)^N)} - P so from this just take common as P then you get
Amount=[P x {(1 + (R/100)^N)-1}].
Ronald said:
5 years ago
12000 in 10% is 1200 then,
12000+1200=13200 is 1st year.
And 13200 in 10% so 13200+3200= 16400.
Same next year we get 16400+6400=18040.
Then, 18040-12000=6040.
Why not like this? Anyone explain to me.
12000+1200=13200 is 1st year.
And 13200 in 10% so 13200+3200= 16400.
Same next year we get 16400+6400=18040.
Then, 18040-12000=6040.
Why not like this? Anyone explain to me.
Vicky said:
1 decade ago
Formula for C.I,
Amount = p(1+R/100)^N, Where amount = Principal + C.I.
Principal + C.I = p(1+R/100)^N.
C.I = p(1+R/100)^N - Principal, ' p ' is a common factor.
C.I = p [(1+R/100)^N-1].
Amount = p(1+R/100)^N, Where amount = Principal + C.I.
Principal + C.I = p(1+R/100)^N.
C.I = p(1+R/100)^N - Principal, ' p ' is a common factor.
C.I = p [(1+R/100)^N-1].
Rahul said:
10 years ago
Brother the answer should be 3852 and a simpler method could be 10 percent of 12000 = 1200 + 10% of 12000 + 10% of 1200 = 1200 + 120 and so on the last will be 1200 + 120 + 12 so grand total 3852.
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