Aptitude - Chain Rule - Discussion

Discussion Forum : Chain Rule - General Questions (Q.No. 9)
9.
A wheel that has 6 cogs is meshed with a larger wheel of 14 cogs. When the smaller wheel has made 21 revolutions, then the number of revolutions mad by the larger wheel is:
4
9
12
49
Answer: Option
Explanation:

Let the required number of revolutions made by larger wheel be x.

Then, More cogs, Less revolutions (Indirect Proportion)

14 : 6 :: 21 : x       14 x x = 6 x 21

x = 6 x 21
14

x = 9.

Discussion:
13 comments Page 1 of 2.

Md.Nazmul Hoque said:   5 years ago
6 cog with 21 revolution cover 6 * 21=126 unit.
14 cog with 9 revolution cover14 * 9=126 unit.
(2)

Niki said:   5 years ago
Solution:

Each revolution of 2nd takes 14/6 =2 with rem2.
By common sense for 21/6 = 3.
Each time we need to add 2 so 3*2 = 6.
Adding both gives 6+3 = 9.
(1)

Vinay vishwakarma said:   7 years ago
Which formula use for this question? please explain anyone.
(1)

Sandeep said:   8 years ago
You can say 6 persons can do a piece of work in 21 days then in how many days 14 person can do the same work.

6*21 =14*x.
=9.
(7)

Sandeep said:   8 years ago
You can say 6 persons can do a piece of work in 21 days than in how many days 14 person can do the same work.

6*21 =14*x.
=9.
(3)

Karthik said:   8 years ago
21 is of small cog then why is it compared with lager ration?

SOUNDARYA said:   9 years ago
@Anonymous.

Because the given cogs are 6 which is less than that of the revolutions 2, which is more.

Anonymous said:   9 years ago
@Rahul.

How is cogs inversely proportional to revolutions?

Prasanna said:   10 years ago
Hi guys,

If you think in another way it would be easy.

Larger wheel has 14 cogs.
Smaller has 6 cogs.

So for one revolution of smaller wheel bigger will rotate 6/14.

1 revolution-----6/14.
21 revolution----21*6/14.

And is 9.
(1)

Pankaj kanaujiya said:   1 decade ago
Lets firstly we take small cog.....
6 cog = 21 revolution
1 cog = 21*6 = 126 revolution
now we have to find the revolution of 14 cog
then
14 cog = 126/14 =63/7 = 9
hence answer is B.
have a good day!!!
(2)


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