# 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

shashibsaini Profile Answers by shashibsaini Questions by shashibsaini

• 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

#### pavitrasp Profile Answers by pavitrasp

• Mar 19th, 2008

9 years...

#### shashibsaini Profile Answers by shashibsaini Questions by shashibsaini

• 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

#### kiranbr Profile Answers by kiranbr

• Jul 8th, 2008

9years

#### meister730 Profile Answers by meister730

• Jul 8th, 2008

1 to 2
2 to 4
4 to 8

at each step it takes 3 years so at the ent step it wud be 9 years

#### Arunjhakhar Profile Answers by Arunjhakhar

• Jul 13th, 2008

9 years

#### sriharsha.ab Profile Answers by sriharsha.ab

• Jul 18th, 2008

1 to 2 - 3 years
2 to 4 - 3 years
4 to 8 - 3 years
______________

- 9 years

#### yogeswari.km Profile Answers by yogeswari.km

• Jun 12th, 2009

12 years 2x=3 then 8x=? 8x*3/2x=12 years

#### bharathmarri Profile Answers by bharathmarri

• Jul 7th, 2009

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

#### sagardesu Profile Answers by sagardesu

• Jan 16th, 2010

Let x be initial amount.
after 3 yrs ----- 2x.
after 6 yrs ----- 4x.
after 9 yrs ----- 8x.

#### reddy6143 Profile Answers by reddy6143

• Feb 9th, 2010

I=(PTR)/100
Money gets 3 times means that the Interest earned is 2 times. So that the amount becomes 3 times (Actual amount + Interest)

2P=(P.3.R)/100;
Now R=(2*100)/3
From this
7P=(P.T.200)/3*100
From this T= 10.5 Years.

#### DAKSHIN619 Profile Answers by DAKSHIN619

• Feb 14th, 2010

If the first amount is 100
After 3 years
100=200
then after 3 years
200=400
then after 3years
400=800

#### sweetuu Profile Answers by sweetuu Questions by sweetuu

• Feb 16th, 2010

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).

#### dpk jain Profile Answers by 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
8p=p(1+t(100/3)/100)
=>  t=21 year

so right ans is 21 year

#### reddy6143 Profile Answers by reddy6143

• 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
R=(P*100)/(P*3)
R=100/3
For the amount to become 8 times, we should earn the interest equal to 7 times the amount.
7P=((PT(100/3))/100
3*700P=PT(100)
T=21 years

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

#### saravanan035 Profile Answers by saravanan035

• Aug 19th, 2010

It is the short cut method.
8=2^3

Amounts doubles in 3 years.
Then for 8 terms=3 (amounts doubles) x3 (this 3 is picked from 8)=9 years

#### coolabhi Profile Answers by coolabhi

• Sep 6th, 2010

9 year

#### prititripathi Profile Answers by prititripathi

• Dec 10th, 2010

let amount b x
so
x*r*3/100=2x (given double itself in 3 yr)
r=200/3

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

=12 yr  