The cost of 3 pens and 21 pencils is equal to the cost of 5 pens and 7 pencils. The ratio of the cost…
The ratio of the cost of a pencil to that of a pen is 1 : 7. If a pen costs p and a pencil costs c, then 3p + 21c = 5p + 7c. Hence 14c = 2p, so c/p = 1/7.
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The cost of 3 pens and 21 pencils is equal to the cost of 5 pens and 7 pencils. The ratio of the cost of a pencil to that of a pen is __________
Answer and explanation
Correct answer D
The ratio of the cost of a pencil to that of a pen is 1 : 7. If a pen costs p and a pencil costs c, then 3p + 21c = 5p + 7c. Hence 14c = 2p, so c/p = 1/7.
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