April 26, 1999
Problem of the Month

Tricky Sequence
by Colin Cole
in the Ask Marilyn column

What is the missing number in this sequence?

20, 22, 24, 26, 30, 33, 40, 44, 120, ___, 11000

Solution to the Problem:

Each number in the sequence represents the number 24 in base 12 down to base 2.

20 is the number 24 written in base 12.
22 is the number 24 written in base 11.
24 is the number 24 written in base 10.
26 is the number 24 written in base 9.
30 is the number 24 written in base 8.
33 is the number 24 written in base 7.
40 is the number 24 written in base 6.
44 is the number 24 written in base 5.
120 is the number 24 written in base 4.
220 is the number 24 written in base 3.
11000 is the number 24 written in base 2.

I guess the next number would be 111111111111111111111111, which is the number 24 written in base 1.

Correctly solved by:

No one

Send any comments or questions to: David Pleacher