If a farmer sells 15 of his chickens, his stock of feed will last for 4 more days than planned, but if he buys 10 more chickens, he will run out of feed 6 days earlier than planned. If no chickens are sold or bought, the farmer will be exactly on schedule. How many chickens does the farmer have?  Pick:
A) 20 B) 50 C) 40 D) 30 E) 60
Let x = total feed required for the planned period   n= number of chicken   t = total time of the planned feed   x = nt   1) x = (n-15) * (t+4)   2) x = (n+10) * (t-6)   equating 1&amp;2   (n-15) * (t+4) = (n+10) * (t-6) or nt+4n-15t-60 =nt-6n+10t-60   10n = 25t   n =5/2 *t or t = 2n/5   x= n *2n/5   substituting this value in 1   n * 2n/5 = (n-15) * (2n/5+4)   2n = 60   n =30   30
<result>D</result>
If a farmer sells 15 of his chickens, his stock of feed will last for 4 more days than planned, but if he buys 10 more chickens, he will run out of feed 6 days earlier than planned. If no chickens are sold or bought, the farmer will be exactly on schedule. How many chickens does the farmer have?