Question

morad and Elias are car mechanics. morad can complete a certain task in x hours. Elias can complete the same task in y hours. which equation correctly describes their combined hourly rate of work ? A) x+y=x+y B) 1/x + 1/y = 1/xy C) 1/x + 1/y = x+y/xy D) 1/x + 1/y = 1/x+y

Answer 1

C) 1/x + 1/y = x+y/x.y is the right answer. Why?

1- Morad will complete his task It's C)   1/x + 1/y = x+y/xy. Why?

Morad complted his task in in "x" hours.  and
 
in 1 hour he will complete 1/x of the task

2- Elias completed his task in in "y" hours.  and 
 
in 1 hour he will complete 1/y of the task:

3- 1/x + 1/y = (x+y)/xy ( reduce to same denominator)