It's a basic algebra.. you dont need to know the meaning of 'r' or 'a'. Let me try.. Q(13) .. f(5) = 75.94  ===> t = 5 so, f(5) = Qo a^5 = Qo(1 + r)^5 = 75.94  -------- (i) and, f(7) = 170.80 ===> t = 7 ; so, f(7) = Qo a^7 = Qo (1 + r)^7 = 170.80  ------(ii) Diving eq (ii) by equation (i); Qo a^7   = 170.80       and    Qo a^7  = Qo(1 + r)^7 ------------     ----------                --------         ---------------------   ------(iii) Qo a^5        75.94                   Qo a         Qo (1 + r)^5 From left side equality, a^2 = 2.249 ==> a = 1.5   ------- (iv) From right equality of eqn (iii) a^2 = (1 + r)^2   r = +- a - 1   ------ (v) use 'a' from eqn (iv) in (v) r = -2.5 and 0.5 I think 'r' can have +ve value only. So, r = 0.5 Try similarly for Question(14) ..:)

ANS · Jan 11, 2011 4:27 PM

Thanks again...

comingsoon · Jan 11, 2011 5:09 PM