Hello, mattty!

You miscounted . . .

Each stroke of a pump removes 8.2% of the remaining air from a container.

What percent of the air remains after 50 strokes?

I originally thought this was simple, use the formula . . . . no

where: .

You should be using: .

Check out the initial condition.

When

Whennoair has been pumped out, the amount is the initial amount,