Charlie can grade exams in 2 hours. It takes Mark 6 hours to grade the same exams. If they work together, how long will it take for them to grade the exams?

I figured it out. 40 minutes. Thanks anyway

1/T = 1/2 + 1/6,

1/T = 3/6 + 1/6,
1/T = 4/6 = 2/3,
T = 3/2 = 1.5HRS.

Angela cam comlete a project in 2 hours. it takes Jason 3 hours to complete the same project. how long will it take for them to complete the project together?

To solve this problem, we can determine their combined rate of grading exams and use that to calculate the time it will take for them to complete the task together.

Let's start by finding their individual rates of grading exams:
- Charlie can grade the exams in 2 hours, so his rate is 1 exam per 2 hours (1/2 exams per hour).
- Mark takes 6 hours to grade the same exams, so his rate is 1 exam per 6 hours (1/6 exams per hour).

To determine their combined rate, we need to add their individual rates:
1/2 exams per hour + 1/6 exams per hour = 3/6 + 1/6 = 4/6 exams per hour.

Now, we can find how long it will take them to grade the exams together using their combined rate:
1 exam / (4/6 exams per hour) = 6/4 = 3/2 = 1.5 hours.

Therefore, if Charlie and Mark work together, it will take them 1.5 hours to grade the exams.