Question

Mark can paint a room in 3 hours, Frank can paint an identical room in 4 hours. How many hours would it take Mark and Frank to paint the room together at their respective rates.?

Answer 1

All you have to do is find the LCD of the number of hours Mark and Frank uses to paint a room.

Mark - 3

Frank - 4

So list the numbers that are a result of a number and 3 and 4

(example: 4 x 1 = 4, 3 x 3 = 9)

3 - 3, 6, 9, 12, 15

4 - 4, 8, 12, 16

The list goes on and on but what we need to get is the LCD so it means it's the least number that 3 and 4 have in common.

3 and 4 both have 12 so The LCD of 3 and 4 is 12.

Another way of finding the LCD could be multiplying the numbers together, but it's not always gonna be the least number. Remember that LCD stands for Least Common Denominator.

How many hours would it take Mark and Frank to paint the room together at their respective rates?

The answer is - 12 hours