Question

The numbers 38, 79, 17, 43, 74, 96, and 87 are re-arranged so that starting with the second number, the tens digit of each number is equal to the units digit of the previous number. What is the fourth number in this new list?

Answer 1

38

Explanation:

Sequential pairs will be ...

38 - 87

79 - 96

17 - 74 or 79

43 - 38

74 - 43

96 - (none)

87 - 74 or 79

We notice that 17 has no preceding number. It must be first in the list. 79 cannot be second, because that skips a bunch of numbers. The sequence appears to be ...

17 - 74 - 43 - 38 - 87 - 79 - 96

The 4th number in the list is 38.