### Brain Teasers

# What's in a Number?

Complete the sequence:

21, 13, 24, 26, ??

21, 13, 24, 26, ??

### Hint

Who needs the decimal system? Sometimes numbers are just slapped together!### Answer

48The first digit of each number is the absolute value of the result of subtracting the preceding number's digits from each other (|2-6|=4), and the second number is the sum of the preceding number's digits (2+6=8).

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## Comments

huh?? I dont speek math

i think it is hard to figure out with just the 4 examples. maybe add a couple more numbers to the series.

21, 13, 24, 26, 48, 412, ??

It is not possible to add a couple more terms for clarity. The next term after 48 has three digits. You can derive a sum from that, but what is the difference of three numbers? The rule is ambiguous for the second digit.

Otherwise, it is a clever finite series. I didn't have the patience to figure it out.

It is not possible to add a couple more terms for clarity. The next term after 48 has three digits. You can derive a sum from that, but what is the difference of three numbers? The rule is ambiguous for the second digit.

Otherwise, it is a clever finite series. I didn't have the patience to figure it out.

If you had a million monkeys pounding on a million calculators you would have a fair description of me trying to figure this out.

Very nice

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