What sum of money invested at 7.5% p.a simple interest for 2 years produces twice as much interest as ₹9600 in 3 years and 6 months at 10% p.a simple interest ?
Answers
SI for 3 yrs = 1200
SI for 1 yr = 400
ie CI for 1st yr = 400
now
CI for 2 yrs = 832
therefore
CI for 2nd yr = (832-400) = 432
since difference between CI for two consecutive yrs is interest for 1 yr on Rs 400
therefore
P= 400 , SI =(432-400) = 32 , T =1
R = 32 × 100
---------- = 8%
400 × 1
now
since SI for 1 yr is 400
therefore
P = SI × 100 400 × 100
----------- = ------------- = 5000
R × T 8 × 1
now to find difference between CI and SI for 3 yrs
we have SI for 3 yrs = 1200
to find CI for 3 yrs.
ise formula
CI = P { (1+R/100)^n - 1}
CI = 5000 { ( 1 + 8/100)^3 - 1 }
= 1298.56
thus
difference of CI and SI
= 98.56
1st case given
P=9600
R =10%
T =3 years or7/2,years
Soln
SI = PXRXT/100
PUTTING THE GIVEN VALUES
SI =9600X7/2X10/100
=96X35=RS3360/-
NOW A/Q
NEW SI is 2 x 3360
=6720/-
Again for new SI
6720,=,PXRXT/100
6720=PX75/10X100X2
6720X100/15=P
THEREFOR P=44800/- IS THE REQUIRED ANS.
Ram