Question

It takes an older employee 13 hours to shovel the snow from a sidewalk, but a younger employee can shovel the same sidewalk in 10 hours. how long will it take them to clear the walk if they work together?

Answer 1

Work in rates per hour. These rates can then be added to form an equation

1/13 + 1/10  = 1/x   where  x is the time for both working together

multiply thru by 130x:-

10 x+ 13 x =  130

x = 130/23 =  5.65 hours  or about  6 hours 39 minutes