Question

Could you use the double fact to find the sum for 4+5? Choose yes or no 4+4=8 Yes or no 5+5=10 yes or no 9+9=18 yes or no

Answer 1

yes.You can use 4+4=8
and then add 1
8+1=9
since 5 = 4+1 we add the 1 at the end