Why does the fact family for 81 and 9 have only two number sentences

It only has two number sentences because 81 divided by anything else wont work only 9 would. Also since 9 times 9 is equal to 81

Because there are only two things you can do with these two "family" members. 81 divided by 9 is 9. 9 times 9 is 81. Strictly speaking, there should be three in the family: 9, 9, and 81 9 is the square root of 81. 81 is 9 squared.