Sue can sew a pre cut dress in 3 hours. Helen can sew the same dress in 2 hours. if they work together, how long will it take them to complete sewing that dress?
Sue sews 1/3 of the dress in one hour
Helen sews 1/2 of the dress in one hour
So.....the portion that they can sew in one hour working together is
1/3 + 1/2 = 5/6
The reciprocal of this tells us how long it will take them working together to complete the dress = 6/5 = 1.2 hours