## Thursday, September 27, 2012

Since many people have trouble with word problems, let's try a few here.

A total of 12,000 is invested in two funds paying 9% and 11% simple interest. If the yearly interest is \$1,180, how much of the \$12,000 is invested at 9% and how much is invested at 11%?

Let's say x dollars are invested at 9% . That means 12,000 - x dollars are invested at 11%. The interest at 9% is x(.09) and the interest at 11% is (12,000 - x)(.11). Add these and set equal to the total amount of interest of 1,180 = .09x + 1320 - 0.11x. 140 = .02x. x= 7000. So 7000 is invested at 9% and 5000 is invested at 11%

How many pounds of M&Ms that cost \$7.50 per pound must be mixed with 24 pounds of Reese's Pieces that cost \$3.00 per pound to make a mixture that sells for \$6.75 per pound?

M&M's 7.50 per pound times x pounds = total cost of 7.50x. The 24 pounds of Reese's Pieces cost a total of 72 dollars. The total mixtures of 6.75 per pound will be 24 + x pounds. So we solve this by takings 7.50x + 72 = 6.75(24 + x). 7.50x + 72 = 162 + 6.75x. 7.50x = 90 + 6.75x. 0.75x = 90, x = 120. You will need 120 pounds of M&M's