You send out 9,000 emails. Of those, 5% are opened. Of those opened, 10% click on a link to register for something. Of those who clicked the link, 20% complete the registration. How many people completed the registration?

You can write 3 equations, solution to each one from top will solve the next one.

5% of 9000= opened

5/100 x 9000 = 450 opened

10% of opened = register

10/100 x 450 = 45 registered

20% of registered = completed

20/100 x 45 = 9 completed (your answer)