I dont understand the question. Can you explain?

Question

At 10am an airplane departs from hanger A, Hanger b, and hanger c. Airplanes depart from Hanger A every 15 minutes, from Hanger B every 18 minutes, and from hanger C every 24 minutes.  How many hours will pass before all three hangers have airplanes departing at the same time again?

Answer 1

You can use the upside down cake method to find the LCM as well:

 

  3 |15  18  24  (find a number that goes into at least 2 of them (3) and divide)

  2 | 5   6   8   (now use 2, obviously for only 6 and 8 as 5 is not divisible by 2)

      5   3   4  

 

now that all the numbers are broken down and not divisible by a number other than 1, multiply in an L shape (easy to remember because you are finding LCM)

 

3 * 2 * 5 * 3 * 4 = 360 minutes (6 hrs)  4 pm.

Answer 2

We need the least common multiple of 15, 18, and 24:

 

15 = (3)(5)

18 = (2)(3)²

24 = (2)³(3)

 

LCM = (2)³(3)²(5) = 360

 

The next time that all three hangars have the same time of departure will be 360 minutes after 10 AM

(i.e., at 4 PM).

Answer 3

Cynthia, we have to find the LCM of 15, 18 and 24.  The plane leaving from hangar A will leave at 10:15, 10:30, etc.

 

You can do the same with the other planes. Instead of working with times, however, we can just do the minutes and let 10:00 be 0.  Hangar B's planes depart at 18, 36, etc.

 

If we list the multiples of 15, 18, and 24, where is the first that they all meet?  Remember that these are in minutes.  You'll have to divide by 60 to turn your minutes to hours, and that'll be your answer.