An event at Super Race Day is the Lawnmower Derby. Team members try to mow a standard-size lawn as quickly as possible.
Terri and Candace can mow the lawn in 18 min. If it takes Candace 30 min to mow a lawn alone, how long does it take Terri to mow the lawn alone?
+526 Terri and Candace can mow the lawn in 18 min.
⇒In 1 min Terri and Candace can mow = \({1 \over 18}\) part of the lawn
Candace alone can mow the lawn in 30 min
⇒ In 1 min Candace can mow = \({1\over 30}\) part of the lawn
So, in 1 min Terri alone can mow \(=({1\over 18} - {1\over 30})\) part of the lawn
\(={12 \over 540}\)
\(={1 \over 45}\)
∴ Terri alone can mow the lawn in 45 min.
~Amy 
