Susan can type 10 pages in 5 minutes. Mary can type 5 pages in 10 minutes. Working together , how many pages can they type in 30 minutes ?

1. 15
2. 20
3. 25
4. 65

Answer: 75

Explanation: Susan 5 minutes 10 pages
Susan 30 minutes (10×30)/5 = 60 pages
Mary 10 minutes 5 pages
Mary 30 minutes (5×30)/10 = 15 pages
60 + 15 = 75 pages