A 30% solution of fertilizer is to be mixed with 60% solution of fertilizer to get 150 gallons of 50% solution. How many gallons of each solution is needed?

Ratio of 30% to 60% solution

= 60-50 : 50-30

= 1:2

Volume of 30% solution

=150 * (1 / (1+2) = 50 gal.

Volume of 60% solution

=150 * (2 / (1+2) = 100 gal

Check: 50+100=150 gal. ok

concentration: (50*.3+100*.6) / 150=75/150=50% ok