If 8 spiders make 4 webs in 9 days, then how many days are needed for 1 spider to make 1 web?
Choose the correct choice from the following answers.
A) 10
B) 20
C) 12
D) 16
E) 18
Explanation:   Let, 1 spider make 1 web in x days.   More spiders, Less days (Indirect proportion)   More webs, more days (Direct proportion)   Hence we can write as   (spiders)8:1   (webs) 1:9}::x:4   â‡’8Ã—1Ã—9=1Ã—4 Ã— x   â‡’x=18   Answer: Option 18
<result>E</result>
If 8 spiders make 4 webs in 9 days, then how many days are needed for 1 spider to make 1 web?