The music class consists of 3 girls and 7 boys. How many ways can a group of 3 be formed if it has to include at least one boy?  Select.
A) 119
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   119ll combinations - three girls = answer   119ll combinations is 10C3 = 120   119ll girls 3C3 = 1   So our answer is   120-1= 
<gadget id="calculator">  120-1</gadget>
<output>119</output>
119   Hence, answer is (119)
<result>A</result>
The music class consists of 3 girls and 7 boys. How many ways can a group of 3 be formed if it has to include at least one boy?