1. Calculate each answer using mental math.
(a) 180% of 50
(b) 50% of 180
(c) 204% of 25
(d) 20% of 650
(e) 80% of 650
(f) 6% of 25
2. You are shopping in a city where the sales tax rate is 9.25%.
(a) How much, including tax, would you pay for a sewing machine that costs $1200?
(b) The sewing machine is on sale for 25% off. If you apply the 25% discount, then the 9.25% sales
tax, then what is the final cost?
(c) What is the final cost if you first apply the 9.25% sales tax, and then the 25% discount?
(d) The machine is on sale for 25% off, and the store offers to pay your sales tax for you. The store
advertises that you saved 25% plus 9.25% for a total of 34.25%. Is this correct?
3. If p is 50% of q and r is 40% of q, then what percent of r is p? (Problem 6.37 in the textbook)
If you are stuck, try testing a value for one of the variables.
4. A factory makes two products, puzzle cubes and puzzle spheres. Unfortunately, 1.5% of the cubes
are defective and 2% of the spheres are defective. They make four times as many cubes as spheres.
What percent of their products are defective?
5. How many pounds of water must be evaporated from 50 pounds of a 3% salt solution so that the
remaining solution will be 5% salt? (Problem 6.38 in the textbook)
If you are stuck, Problem 6.19 may help.
6. In the NBA, teams take 2-point and 3-point shots. In an NBA playoff game (April 27, 2011):
• The Spurs made 32 of 63 2-point shots and 7 of 22 3-point shots.
• The Grizzlies made 38 of 77 2-point shots and 3 of 10 3-point shots.
(a) Which team was better at making 2-point shots?
(b) Which team was better at making 3-point shots?
(c) Which team had the better overall shooting percentage?
7. A store wants to tell everyone they are having a 100% off sale. They’re not, but they are going to
give a set of discounts that add up to 100%.
(a) One option would be to take 50% off twice. If this happens, a sale item will cost what percent
of the original?
(b) Another option would be to take 40% off, then 60% off. If this happens, a sale item will cost
what percent of the original?
(c) Another option would be to take 25% off four times. If this happens, a sale item will cost what
percent of the original?
(d) Think of some better ways the store could set their discount. Is there a best possible way, one
that still lets them sell items for as much as possible?
Thank you!!
