SOLUTION: On average, it takes a teacher 39 minutes to grade a set of quizzes. It takes her teacher's aide twice as long to do the same grading. How long will it take if they work together

Algebra ->  Rate-of-work-word-problems -> SOLUTION: On average, it takes a teacher 39 minutes to grade a set of quizzes. It takes her teacher's aide twice as long to do the same grading. How long will it take if they work together      Log On


   



Question 286877: On average, it takes a teacher 39 minutes to grade a set of quizzes. It takes her teacher's aide twice as long to do the same grading. How long will it take if they work together to grade a set of quizzes?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
You need to add their rates of working to get
their rate working together
Let t = their time to finish working together
given:
1st teacher's time is 39 min
teacher's aide's time is2%2A39+=+78 min
In words:
(1 set of quizzes/teacher's time) + (1 set of quizzes/aide's time) = (1 set of quizzes/time working together)
1%2F39+%2B+1%2F78+=+1%2Ft
multiply both sides by 78t
2t+%2B+t+=+78
3t+=+78
t+=+26
It will take them 26 min working together