Today's mentalfloss.com **Brain Game** *Think Thursday* challenge is a throwback that we offered nearly five years ago. It's still a good one!

What's the next letter in this sequence?

K, M, G, T, P, ?

*Here is the SOLUTION.*

**SOLUTION:**

The letters represent "the first six entries in the International System of Units prefixes for unit multiples." But if you don't speak geek:

*They stand for 1,000 times the previous unit of measurement.*

*base unit
K = kilo (1,000 units)
M = mega (1000K units)
G = giga (1000M units)
T = tera (1000G units)
P = peta (1000T units)... then our answer is:
E = exa (1000P units).*

**NOTE:** In binary systems (like those used for computer memory), the multiple is 1024 instead of 1000, but the prefixes are the same. Thanks for playing! Tomorrow, it's *Free-for-All Friday!*