## umar284 3 years ago -7,-5,-3,-1,0,1,3,5,7 How many distinct products can be obtained by multiplying pairs of numbers from the list above? A)9 B)17 C)19 D)21 E)31

1. RoamingBlue

2. umar284

Actually its B)17

3. RoamingBlue

49, -49, 35, -35, 21, -21, 7, -7. 25, -25, 15, -15, 5, -5, 9, -9, 3, -3, 1, -1, 0 I count 21 ... which 4 don't you think belong?

4. umar284

wait just a minute

5. umar284

im typing the solution

6. RoamingBlue

oh wait, I see, the four that don't belong are 49, 25, 9, and 1

7. umar284

your right! how did you figure that out?

8. RoamingBlue

because you cannot get positive 49 from any of the combinations you would need to multiply -7 times -7 or 7 times 7 to get a positive result

9. RoamingBlue

and you only have one negative seven and one positive seven ... so there's no way you can multiply two sevens (from your list) to get a positive ... it can only be negative

10. umar284

and the others? 25,9 and 1?

11. RoamingBlue

for the same reason ... you can't get 25 because your fives are positive and negative, and you always get negative when you multiply positive by negative ... same for 9 (threes) and 1 (ones)

12. umar284

great,thanks

13. RoamingBlue

do you see why, or should I explain it more ... I sorta botched the whole initial explanation thing ;)

14. umar284

nah i think i got :)

15. RoamingBlue

awesome :D