Question

Rita,krish and zara start solving a puzzle together. They take 12,18 and 21 minutes respectively to solve the puzzle. After how much time will they start solving a new puzzle together

Answer 1

To answer this question you will use the least common multiple of the time the three girls use. 
Find factors for each time.

Rita= 12 mins 
Krish= 18 mins

Zara = 21 mins 

least common multiple for 12, 18, 21  = 252

That is 252 minutes which is 4 hours 12 minutes

Therefore the next time they will solve a puzzle together will be after 4 hours 12 minutes.
 

Answer 2

Answer:

4 hour 12 mins

Step-by-step explanation:

Rita = 12 = 2 x 2 x 3

Krish = 18 = 2 x 3 x 3

Zara = 21 = 3 x 7

therefore,

LCM(21,18,12) = 252

thus 252 minutes

or

4 hour 12 mins