I need help understanding this problem

Question

I dont understand this equastion. I understand the formula but everytime i work this problem out or any simialr to this my answer is always wrong...

 

Answer 1

Work done, W = Pt

Here, P is the power and t is the time.

Convert time units from min to sec

90 min = 90*60 sec

            =5400 sec

Substitute 100 W for P and 5400 sec for t.

w = 100 * 5400

   = 540,000 J