When Professor Sum was asked by Mr. Little how many students were in his classes, he answered, “All of them study either languages, physics, or not at all. One-half of them study languages only, one-fourth of them study French, one-seventh of them study physics only, and 20 do not study at all.” How many students does Professor Sum have?
math - PsyDAG, Tuesday, December 8, 2009 at 10:15am
1/2 + 1/4 + 1/7 = X - 20
Solve for X.
I hope this helps.