A store sells two different types of coffee beans; the more expensive one sells for $8 per pound, and the cheaper one sells for
$4 per pound. The beans are mixed to provide a mixture of 50 pounds that sells for $6.40 per pound. How much of each type of coffee bean should be used to create 50 pounds of the mixture?
You can use Guess and Check and divide the 50 pounds into 2 parts. Multiply the price for both and do square root for the prices. Then at the 2 square roots and see if they add up to $6.40. If not, then divide the 50 pounds into something else, like 30 and 20 or something like that.