David Rock's House Number

David's house has a number.

1) If the house number is a multiple of 3, then it is a number from 50 to 59

2) If the house number is NOT a multiple of 4, then it is a number from 60 to 69

3) If the house number is NOT a multiple of 6, then it is a number from 70 to 79

What is the house number?

Note: Conditions 1), 2), and 3) must all be satisfied.

Extensions

Will the problem have a unique solution if the interval in 3) is changed from 80 to 89?

Can you

createsimilar problems with other intervals, having unique solutions?

Who is

David Rock?David is a mathematics educator who happens to be Dean, College of Education, University of Mississippi. He is co-author of

, one of the most widely used current mathematics methods textbooks.Teaching Secondary Mathematics