The music class consists of 5 girls and 7 boys. How many ways can a group of 3 be formed if it has to include at least one boy?
Select the correct option.
A) 155	B) 158	C) 161	D) 165	E) 210
Reverse combinatorics approach is preferred method on this one   Note that at least 1 boy gives clue to using this method   All combinations - five girls = answer   All combinations is 12C3 = 220   All girls 5C3 = 10   So our answer is   220-10= 
<gadget id="calculator">  220-10</gadget>
<output>210</output>
210   Hence, answer is (210)
<result>E</result>
The music class consists of 5 girls and 7 boys. How many ways can a group of 3 be formed if it has to include at least one boy?