A deck of 320 punched cards can be read by one reader in 20 minutes. A second reader can read the same deck in 12 minutes. How many minutes would it take both readers working together to read a deck? How long would it take to process the deck of cards in example one if the first reader stopped working
after 5 minutes?

Question

A deck of 320 punched cards can be read by one reader in 20 minutes.  A second reader can read the same deck in 12 minutes.  How many minutes would it take both readers working together to read a deck? How long would it take to process the deck of cards in example one if the first reader stopped working 
after 5 minutes?

anonymous · Answer

For the first part i got 7.5 minuets.
But for the second I couldn't figure out anything