allerySix pens cost Rs 90 at a fixed price per pen. What do 10 pens cost?
ARs 150
BRs 120
CRs 54
DRs 900
Answer & Solution
Correct answer: A. Rs 150
1. Cost is directly proportional to the number of pens, so cost / pens is constant.
2. 90 / 6 = Rs 15 per pen.
3. 10 pens cost 10 x 15 = Rs 150.
_Source: Wikipedia, Proportionality (mathematics), lead section_
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