An amount doubles itself in 3 years.

An amount doubles itself in 3 years. When This amount can become 8 times of itself?
This question is related to TCS Interview

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  • Member Since Aug-2006 | Mar 27th, 2008

Suppose Amount Was Rs 100.00 In 1st Year

1 To 3 Yrs - 200
4 To 6 Yrs - 400
7 To 9 Yes - 800

Answer is 9 Yrs

Showing Answers 1 - 17 of 17 Answers

Let 'x' be the amount.

& this amount doubles itself in 3 years [Given]

i.e; x --  2x in 3 yrs

i.e; 2x = 3

=> 8x = 12

Therefore, this amount become 8 times itself in 12 years

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  • Feb 9th, 2010

Money gets 3 times means that the Interest earned is 2 times. So that the amount becomes 3 times (Actual amount + Interest)

Now R=(2*100)/3
From this
From this T= 10.5 Years.

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Since, amount goes double in 3years,
let us consider, starting amt is x rupees,
according to question. it get doubles in next 3 years.
therefore, after 3 year it will be 2x rupees.
In 6 years it will be 4x rupees and in next 9 years it will be 8x rupees.
Hence, in 9 years total amount will be 8 times of strating amount(x).

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dpk jain

  • May 10th, 2010

According to me all those which are saying that ans is 9yrs, are wrong.

ans would be 9yrs if there is condition that interest is compounded 2 yearly.
that means after each 2 year total amount(principle amount+interest) will be taken as principle amount.

but such condion is not here.
so it is quest of simple interest.

solution is

let amount is p and rate of interest is r then
A/Q   2p=p(1+3r/100)
=>  r=100/3

let amount become 8 times in t year
=>  t=21 year

so right ans is 21 year


  • May 23rd, 2010

An amount doubles itself in 3 years mean that the interest earned for 3 years is equal to the amount. Therefore the rate of interest R is
For the amount to become 8 times, we should earn the interest equal to 7 times the amount.
T=21 years

Therefore it takes 21 years to make 8 times the original amount in the dive context.

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let amount b x
 x*r*3/100=2x (given double itself in 3 yr)

x*200*t/3*100=8x (asked in how many yr it will b 8 time of itself where r=200/3)

=12 yr

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