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Asked by Kchawla94 | 05 Apr, 2019, 06:03: PM
Simple interest triples the investment in 4 years.

if p is principle and  r is rate of interest per year, we have      p×4r/100 = 2p     or   r = 50%

If the amount with simple interest becomes 6 times of itself  in n years,
we have   p×n×50/100 = 5p  or number of years n = 10

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Compound interest doubles the investment in 4 years.

if p is principle and R is rate of interest per year ,  we have   p[ 1 + (r/100) ]4 =  2p    or  [ 1 + (r/100) ] = 21/4 ....................(1)

if amount with compound interest becomes 4 times of itself in n numer of years, we have  p[ 1 + (r/100) ]n =  4p .................(2)

after simplification, eqn.(2) becomes,  [ 1 + (r/100) ]n =  4 ...................(3)

Using eqn.(1),  we rewrite eqn.(3) as  2n/4 = 22   or    number of years n = 8
Answered by Thiyagarajan K | 06 Apr, 2019, 02:45: PM

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