From 6 positive numbers and 7 negative numbers, how many groups of 4 numbers, yielding a positive product, can be formed? Choose the correct option: A) 720 B) 625 C) 230 D) 365 E) 255
The number of ways to choose 4 positive numbers is 6C4 = 15.   The number of ways to choose 4 negative numbers is 7C4 = 35.   The number of ways to choose 2 positive and 2 negative is 6C2*7C2 = 15*21= 
<gadget id="calculator">15*21</gadget>
<output>315</output>
315.   The total number of groups is 15+35+315= 
<gadget id="calculator">15+35+315</gadget>
<output>365</output>
365.   The answer is 365.
<result>D</result>
From 6 positive numbers and 7 negative numbers, how many groups of 4 numbers, yielding a positive product, can be formed?