Question

₹ 9000 becomes ₹ 18000 at simple interest in 8 years. Find the rate per cent per
annum.

Answer 1

GIVEN:

Principal (P) = Rs. 9000 

Amount (A) = Rs. 18000

Time (T) = 8 years

SOLUTION:

Simple Interest (S.I.) = A - P

S.I.= 18000 - 9000  = 9000

Since,

S.I = (P × R × T)/100

Therefore,

9000 = (9000 x R x 8)/ 100

9000 x 100 = 72000 x R

900000 = 72000 x R

900000/ 72000 = R

25/2 = R

R = 12.5 %

Ans: The rate if interest per annum is 12.5 %..

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Answer 2

p = rs 9000 ; A = rs 18000 ; t = 8yrs

p+ si = A => 9000 + (9000*8*r/100) = 18000

=> (9000*8*r/100) = 9000 => r = 9000 *100/8*9000 => r = 12.5

•°• r = 12.5%