Robert can cut the grass in 16 hours. Mary can cut the grass in 24 hours. If they work together, Mary starts 4 hours before robert, how long will mary work?

Question

asked Oct 20, 2024 171k views

1 Answer

Anqi Lu · Answer 1 · 2024-10-27T03:29:29+0000

Answer:Mary works 18 hours

Explanation:

1.Robert takes 16 hours to cut the grass, and Mary takes 24 hours.

2. Mary starts 4 hours before Robert, so when Robert starts, Mary has already been working for 4 hours.

3. Let's say Mary works for x hours after Robert starts.

4. Since Mary works for 4 hours before Robert starts, the total time they work together is x + 4 hours.

5. In that time, Robert works for x hours.

6. Together, they complete the job, so the total time it takes to finish the job is 16 hours (Robert's time) + 24 hours (Mary's time).

7. Therefore, we can set up the equation: x + 4 + x = 16 + 24.

8. Simplifying the equation, we get: 2x + 4 = 40.

9. Subtracting 4 from both sides, we get: 2x = 36.

10. Dividing both sides by 2, we get: x = 18.