The music class consists of 4 girls and 6 boys. How many ways can a group of 3 be formed if it has to include at least one boy?
Choose the correct answer.
A) 116  B) 158  C) 161  D) 165  E) 172
Reverse combinatorics approach is preferred method on this one   Note that at least 1 boy gives clue to using this method   116ll combinations - four girls = answer   116ll combinations is 10C3 = 120   116ll girls 4C3 = 4   So our answer is   120-4= 
<gadget id="calculator">  120-4</gadget>
<output>116</output>
116   Hence, answer is (116)
<result>A</result>
The music class consists of 4 girls and 6 boys. How many ways can a group of 3 be formed if it has to include at least one boy?