Riddle of the week

 

Riddle of the week.

 

 What should the last entry be in the following sequence of numbers ... 9|18, 8|46, 7|94, 6|63, 5|52, 4|__?

 

ANSWER:

Each sequence represents the square root of a number with digits reversed (9 is the square root of 81, 8 is the square root of 64, and so on)... So the missing number is 61 (4 is the square root of 16).