How much could Able harvest in one day? How much could Barney harvest? How much could Charlie harvest?

Then how much could they harvest together in one day?

Then how many days do they need?

Google results for "work word problems"

Going out of order:

Use the following set-up:

. . .liters solution:

. . . . .60%: 40

. . . . .water: w

. . . . .40%: 40 + w

. . .percent acid:

. . . . .60%: 0.6

. . . . .water: 0

. . . . .40%: ??

. . .liters acid:

. . . . .60%: 0.6(40) = 24

. . . . .water: 0(w) = ??

. . . . .40%: ??

Complete the table. Use the fact that the amount of acid in the two inputs must equal the amount of acid in the mixture. Sum the first two expressions, set equal to the third, and solve the resulting linear equation.

Google results for "mixture word problems"

This one works just like the previous exercise, except that you'll be adding a 100% input (because "pure" means "entirely") rather than 0% (because "water" meant "none").

Have fun!