Aptitude - Chain Rule - Discussion

7 spiders in 7 days make 7 webs

Since 7 webs in 7 days.....1 web in 1 day..dis 1 web is made by 7 spiders.

Now,
Since 7 spiders have made 1web in a day
divide this 1 web into 7 parts 1 each for every spider..

So 1 spider will make 1/7 part of the web in a day.

Now,

1/7 th part completes in 1 day
so 1/7(1st day) + 1/7(2nd day) + 1/7(3rd day) + 1/7(4th day) + 1/7(5th day) + 1/7(6th day) + 1/7(7th day) = 7/7 = 1 complete web by a spider...

Thus it took 7 days which is the answer.

Take this example.

7 girls make 7 cakes in 7 days.
so 7 girls complete 1 cake in 1 day.
7 girls complete 2cakes in 2days.
7 girls complete 3 cakes in 3 days.
Similarly, 7 girls make 7 cakes in 7 days.

Simply can say effort of 7 girls is needed for 1 cake to complete in 1 day as good as saying effort of 1 girl is required for 7 days to make 1 cake.

@Radhika.

You explained it very well. Thanks.

The correct Answer is 1.

3 chickens can make 3 eggs in 3 days, then how many eggs can be made by 300 chickens in 300 days?

@Radhika.

Superb explanation, Thank you.

7 Spiders make 7 Webs in 7 Days. -> eq 1
7 Spiders make 1 Web in 1Day -> eq 2
1 Spider make 1 Web in X=? Days) -> eq3

Multiple Value of Number of Spiders with a number of days from eq 2 and eq3

7*1. = 1*X.
X. =. 7*1/1,
X. = 7 -----> Ans.

Less Spiders -> More Days (Indirect Proportion).
Less Webs -> fewer Days (Direct Proportion).

Nice. Thanks all.

Nice explanation @Radhika.

Good explanation @Radhika.