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Answer:
(a) Store A: (2, 40¢), (1, 20¢); Store B: (2, 30¢), (1, 15¢)
(b) Store A: 20¢; Store B: 15¢; A's cost more
(c) A: $1.00; B: $0.75
Step-by-step explanation:
If you have done any personal shopping, you are probably aware that the cost of 4 items is 4 times the cost of 1 item. If you are at all familiar with your multiplication tables, you probably know that ...
2 = 2×1
4 = 2×2
6 = 2×3
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(a) This knowledge makes it fairly easy to fill in the tables in part (a) of this question.
Store A
The cost of 4 pens is 2 times the cost of 2 pens. The cost of 2 pens will be half the cost of 4 pens, so will be 80¢/2 = 40¢. Similarly, the cost of 1 pen will be half the cost of 2 pens, so will be 40¢/2 = 20¢. Now the table looks like ...
Pens, Cost
4, 80¢
2, 40¢
1, 20¢
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Store B
The cost of 6 pens is 3 times the cost of 2 pens, so the cost of 2 pens will be 1/3 of 90¢, or 30¢. The cost of 1 pen is half that, 15¢. So the table for Store B looks like ...
Pens, Cost
6, 90¢
2, 30¢
1, 15¢
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(b) As we have seen above, the charge for 1 pen is ...
Store A: 20¢
Store B: 15¢
Store A's pens cost more.
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(c) The cost of 5 pens can be figured a number of ways. One way is to simply multiply the cost of 1 pen by 5. You can also add the cost of 1 pen to the cost of 4 pens, or subtract the cost of 1 pen from the cost of 6 pens.
5 pens from Store A = 5 × 20¢ = 100¢ = $1.00
5 pens from Store B = (cost of 6) - (cost of 1) = 90¢ -15¢ = 75¢ = $0.75
