pre algebra story problem

Question

the cost of mailing a dvd in an envelope by express mail is equal to the cost of mailing a dvd in a box by priority mail. what is the weight of the dvd with it's packing material? the box costs $2.25 and is $2.50 per lb to mail. the envelope costs $1.10, and costs $8.50 per lb to mail it.

Answer 1

Let w represent the weight of the DVD.  Then the cost to mail it in an envelope by express mail will be 1.10+8.50w.  The cost to mail it in a box via priority mail will be 2.25+2.5w.  Since the cost either way is the same, just equate the two expressions:

 

1.10+8.50w=2.25+2.50w

6w=1.15

w=.192 (Approx.)

 

So, the DVD (with packing) weighs approximately 0.192 pounds.