How to calculate "K"

i will try to explain you via steps

step 1: calculate P by taking k=18% the answer will come as P=20.22

step 2: calculate P by taking k=19% the answer will come as P=17.87

step 3: use formula of interpolation that is: lower rate + [(p of lower rate-desired p) / (p of upper rate-p of higher rate)] * (higher rate-lower rate)

in this case it vil b as follows: 18% + [(20.22-20) / (20.22-17.87)] * (19%-18%)

which is  18% + (0.22/2.35) * 1 wchich comes to 18.10%

as in exams we dont know k straightaway, so whtevr d value of k is taken if interpolation formula is applied properly the answer will come the same

i hope this helps

thk u so much sneha..i've posted this two times no body replied..thks for explaining..

i didnt get one point..are u assuming k as 18% and 19% ?if yes how assuming??pls explain

thks in advance

well there is no way to guess the accurate value of  "k" at first tym itself....u have to use different rates in order to get nearest value to p n then use interpolation.