A grocer has two kinds of candies, one selling for 40 cents a pound and the other for $1.40 per pound. How many pounds of each kind must he use to make 100 pounds worth 85 cents a pound?

Answer: 55 lbs of $0.40 and 45 lbs of $1.40

Step-by-step explanation:

Let's say that we have two buckets, one that weighs x pounds and the candies in it are $0.40 per pound and another that weighs 100-x pounds (because we know the two added together must be 100 pounds) and the candies in it are $1.40 per pound.

There is a third bucket that is made when you combine the two, it weighs 100 pounds and the candies in it are $0.85. Multiply the cents per pound by the pounds of the candy for each bucket and you get this equation:

0.4 * x + 1.4 (100-x) = 0.85 * 100

Solve!

0.4x + 140 - 1.4x = 85

-x + 140 = 85

-x = - 55

x = 55

From this we get that 100 - x = 45.

So, the answer is 55 lbs of $0.40 and 45 lbs of $1.40