Two teachers are grading math homework. One teacher can grade a stack of papers in 50 minutes and the other can complete the job in 100 minutes. How long does it take them to grade all the papers if the first teacher grades alone for 23 minutes, then they work together to finish?
Let time taken for both to grade the remaining papers be T
Then time (singly and in tandem) taken by the 1st = T + 23
We then get: =======>
T + 2T + 46 = 100 ------ Multiplying by LCD, 100
3T = 54
Time taken by both to complete job, or
Time taken to grade ALL =