find amount of minutes

Question

Typist X can type 20 forms per hour and Typist I can type 30 forms per hour. If there are 30 forms to be typed and both typist are put to work on the job, how soon should they be expected to finish the work?__________minutes.

Answer 1

X types 1 form every 3 minutes, therefore X types 1/3 of a form per minute

Y types 1 form every 2 minutes, therefore Y types 1/2 of a form per minute

 

Both work for "m" minutes

 

m/3 + m/2 = 30             30 forms must be typed

2m + 3m = 180

5m = 180

m = 36

 

Working together they type 30 forms in 36 minutes.

Answer 2

X types 20 forms every hour, or 1 form every 3 minutes (60/20)

l types 30 forms every hour, or 1 form every 2 minutes (60/30)

the LCM of 2 and 3 is 6

every 6 minutes X types 2 forms

every 6 minutes l types 3 forms

every 6 minutes X and l together type 2+3=5 forms

30/5=6 groups of 6 minutes equals 6*6=36 minutes to finish the job

6 minutes, 5 forms

12 minutes, 10 forms

18 minutes, 15 forms

24 minutes 20 forms

30 minutes, 25 forms

36 minutes, 30 forms