# A sum of money amounts to rs.1008 in 2 years and amounts to rs.1164 in 3 1/2 years @ simple interest. find principal and rate of interest

2
by sravanthi96

2014-08-10T20:19:38+05:30
Sample interest for 3/2 years = 1164-1008 = 156
sample interest for 2 years = 156*4/3 = 208
principal amount = 1008-208 = 800Rs.
208 = 800*r*2/100
208 = 16r
r = 13
rate of interest = 13% year

whether this is correct??/
may i know how 4/3 comes in second step ??
2014-08-10T20:25:25+05:30

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Total amount = Rs 1008 = P + P * r * 2  = P ( 1 + 2 * r)      equation 1

Total amount =  Rs 1164  = P + P * r * 3.5 = P ( 1 + 3.5 r )    equatio n  2

Subtract 1st equation from 2nd equation and cancel P,
P * 1.5 * r = Rs 156
P * r = 104
1st equation is :   P + 2 P r = 1008      substitute value of  P * r
P + 2 * 104 = 1008
P  = Rs 800
r = 104 / 800 =    0.13     =>  rate of interest is 0.13 * 100  =  13 %

whether s perfectly crct >???
perfect and easy to understand too.
thank you sooo much