Question

Mary can type six letters in 20 minutes, Maggie can type five letters in 20 minutes, and Su Ying can type two letters in 20 minutes. Working together, and assuming that each letter is of the same length, how many minutes will it take them to type 45 letters?

Answer 1

70 minutes

Explanation:

Mary can type the number of letters in 20 minutes = 6

Maggie can type the number of letters in 20 minutes = 5

Su Ying can type the number of letters in 20 minutes = 2

Working together they can type the number of letters in 20 minutes

= 6 + 5 + 2

= 13 letters

Working together they can type the number of letters in 1 minute =
`(13)/(20)`

To type 45 letters time taken by them =
`(45)/((13)/(20) )`

=
`45* (20)/(13)`

=
`(900)/(13)`

= 69.230 ≈ 70 minutes

It will take them 70 minutes to type 45 letters.