An assembly line worker at Rob's Bicycle factory adds a seat to a bicycle at the rate of 2 seats in 11 minutes. Write a proportion relating the number of seats s to the number of minutes m. At this rate, how long will it take to add 16 seats? 19 seats?

1) ratio of number of seats to the number of minutes: 2 seats / 11 minutes

2) proportion relating the number of seats s to the number of minutes m:

s / m = 2 seats / 11 minutes

3) How long will it take to add 16 seats

16 seats / x = 2 seats / 11 minutes

=> x = 16 seats * 11 minutes / 2 seats = 88 minutes

4) How long will it take to add 19 seats:

19 seats / x = 2 seats / 11 minutes

=> x = 19 seats * 11 minutes / 2 seats = 104.5 minutes.