mathematics
posted by AT on .
Jim paid $3.99 for a 14ounce bag of cookies. What was the
unit cost per pound?

$3.99 / (14/16 lb) = (8/7)*($3.99) = $4.56/lb

More than one way to skin a cat. Proportions come up a lot and this can be solved as one.
State the relationship you need verbally.
"3.99 is to 14, as x is to 16"
Then set up a proportion.
3.99 x
 = 
14 16
Crossmultiply, giving:
14x = 16(3.99)
Divide both sides by 14, giving:
x = (16/14)3.99
Reduce:
x = (8/7)3.99
Finally, you need to pull out your calculator.
x = 31.92/7
x = 4.56
That is the cost per 16 ounces: that is, per pound.