Word Problem 5 (Wheels and revolutions times)
Problem 5: Three wheels making 60,36,24,revolutions in a minute start with a certain point in their circumferences downward. They will first come all together again in the same position after;
a. 5 seconds b. 6 seconds c. 30 seconds d.15 seconds
— Shapes and volumes — math aptitude test –
Solution:
Three wheels making 60 revolutions in a minute start ……
All three wheels make respective revolutions in a time of one minute or 60 seconds.
Lets take wheel which completes 36 revolutions in a minute !
Similarly 1 revolution time for the wheel with 60 revolutions in one minute is !
and
1 revolution time for the wheel with 24 revolutions in one minute is !
Now we arrange 1 revolution time for all three wheels as;
,
,
,
,
Now we find that LCM of numerators i-e 10, 6 and 15 is 30 and LCM of denominators i-e 6,6, and 6 is 6
So using formula;
we get;
So, after 5 seconds all three wheels will come at the same position
