let the two ducks be a(10 km/h) and b(18 km/h).
given that radius of pond= 7km . so circumference = 44 km.
they move in opposite direction means one clockwise and one anti clockwise and as they are diametrically opposite.
let a travels x km before they meet so b will travel (22-x) km.
as time will be equal so making equation 1 for meeting first time.
=> ( x/10)=((22-x)/18)
=>x=(55/7)
=> t1(time for 1st meeting) =speed of a *time = 0.78hr
now for meeting 2. let a travels y distance b travels (44-y).
==> (y/10)=((44-y)/18)
=>y=110/7
=>time taken(t2) = speed of a *time = 110/70 = 1.57hr
total time = t1+t2 = (.78 +1.57)= 2.35hrs