Question 63261

Let x lb of the first type be mixed with y lb of the second type.
Then x + y = 100 --------------------(1)

Cost of x lb at $9 per lb = $ 9x
Cost of y lb at $ 12 per lb = $12y
Cost of 100 pb of the mixture = 100 * 11.25 = 1125

==> 9x + 12y = 1125 ------------------(2)
    9x + 9y = 900 -----------------(1) x 9

Subtracting the above two equations we get...

     3y = 225
==> 3y/3 = 225/3
==> y = 75

PLugging in y = 75 in (1) we get.. x = 25

Thus he has to mix 25 lb of $9 type with 75 lb of $ 12 type to get the required mixture.


Good Luck!!!