Posted by **stacey** on Thursday, November 10, 2011 at 6:57pm.

in a class of 30 students, 17 have computers at home and 20 have cassettes. If 4 students in the class have neither a computer or a cassette, how many of the 30 students have both?

- math -
**Steve**, Thursday, November 10, 2011 at 7:24pm
If you count all the students with computers, and then count all those with cassettes, you count twice the ones that have both. So, adjust the total accordingly.

30 students. 4 with nothing, leaves 26 with either computer or cassette or both

17+20 = 37, but there are only 26 students available, so there must be 37-26=11 with both. Just adding up the numbers counted 11 of them twice.

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