Jim hits the target 90 out of 100 times.

Charlie hits the target 80 out of 100 times.

If both fire once, what is the probability that the target is hit?

[Check your answer in decimal form]

The possibilities that need to be added together are:
Jim hits, Charlie misses
Charlie hits, Jim misses
They both hit

(.9)(.2) + (.8)(.1) + (.9)(.8) = 0.98

There is a 98% chance that the target is hit.