Question

The CI on a certain sum for 2 years is Rs 41 and SI is 40rs . THEN the rate per annum is

Answer 1

Let the principal be = P
     rate of interest  = t
                 time  n = 2
We have CI = P(1+t )² - P = 41       ---- (1)
              SI = P*t*2=40
                  = P*t  = 20                 ---- (2)
Solving (1)  P(1+t²+ 2t) -P =41
⇒ P + Pt² + 2Pt - P= 41
⇒ Pt(t + 2)  = 20 (t+2) = 41  substituting value of t from (2)
⇒ t +2 = 41/20
⇒ t = 1/20= 5/100= 5%
Rate per annum is 5%