# a)In how much time will simple interest on a sum of money be 2/5th of the sum, at the rateof 10% per annum b) At what rate of interest will simple interest be half the principal in 5 years. c)A sum of money amounts to Rs. 1265 in 3 years and to Rs.1430 in 6 years, at simpleinterest. Find the sum and the rate percent.

2
by nandhinimouli

2014-09-25T16:39:43+05:30
Let the sum of money = A

P = Principal amount
R = Rate percent
T = Time
a).⇒A/Q,
S.I of sum = 2/5 of sum

therefore time = 4 years

b).⇒A/Q,
S.I = 1/2 of principal amount in five years

therefore Rate = 10%per annum

c).⇒Sum of money (A) = (P+S) ,where P = principal amount   and S is S.I of three years
A/Q,
Sum of money in 3 years() = 1265
or   P+S = 1265  -------(1)
Sum of money in 6 years () = (P+2S)
or,   P+2S = 1430  --------(2)
Now ,Equation (2)-(1) ,,
S = 165 = S.I of three years
then P = 1100  = principal amount
now,

therefore Rate = 5%
2014-09-25T17:15:15+05:30
A) let the sum of be x
2x/5=x*10*t/100
⇒2=10t/20
⇒t=4 yrs

b)let the principal be x
si=x/2
x/2=x*5*r/100
⇒50=5r
⇒r=10%

c) amt after 3 yrs=P+I=1265..........(i)
amt after 6 yrs=P+2I=1430............(ii)
subtracting (ii) frm (i)
we get I=165
substituting in eqn (i)
we get,P+165=1165
⇒P=1100
165=1100*r*3/100
⇒r=5%