Question

It takes two hours for a person X to mow the lawn. Y can mow the same lawn in four hours. How long (in minutes) will it takes X and Y, if they work together to mow the lawn?

• A.
  $90$
• B.
  $60$
• C.
  $80$
• D.
  $120$

Answer 1

The correct option is C

$80$
$WorkdonebyXin1hour=\frac{1}{2}$

$WorkdonebyYin1hour=\frac{1}{4}$

$WorkdonebyXandYtogetherin1hour$

$=\frac{1}{2}+\frac{1}{4}=\frac{3}{4}$

$\therefore Totaltimetocompletemowingoflawn$

$=\frac{4}{3}hour$ $=\frac{4}{3}\times 60=80min$