If 7 spiders make 7 webs in 7 days, then 1 spider will make 1 web in how many days? Choose the correct choice from the following answers:  A) 7  B) 6  C) 5  D) 4  E) 3

Rationale: let the required number days be x . less spiders , more days ( indirect proportion ) less webs , less days ( direct proportion ) spiders 1 : 7 webs 7 : 1 1 x 7 x x = 7 x 1 x 7 = > x = 7 answer is 7
Answer: A