probability and statistics

Question

forty percent of the sales force at large company have laptop computers, 65 percent have desktop computers, and 24 percent have both. what percent of the sales people have laptop or desktop computers?

Answer 1

If the sales force is 100 staff then we can substitute for the percentages: 40 have laptops, 65 have desktops, and 24 have both.

Consider the following sets:

A those with laptops only

B those with desktops only

C those with both

A+C=40 represents those that have laptops;

B+C=65 represents those that have desktops;

C=24 represents those that have both, so A=40-24=16, B=65-24=41.

Those having either a laptop or a desktop=A+B=16+41=57.

Converting this to a percentage: 57% have either a laptop or a desktop (but not both).