It’s 1.
Explanation: you need to find the greatest factor that works out for them both. You can cross out 4 and 8 because no other whole number can be multiplied to get 15, and it’s not 3 since you can’t multiply it with a whole number to get 64. 1 works for them both.
5. Positive
6. Negative
7. Negative
8. Positive
9. No correlation
10. Positive
11. No correlation
12. Positive
4+15+11+5+7+10= 50 cm
10cm was the missing one
