# Replace the question marks

Here's some number problems.

8:2::1:1::64:?

A:4::D:49::?:169

439: SQUARE::125:CUBE::216:?

A:8::M:5::J:1::O:10::M:?

First one

8:2::1:1::64:4
First number is the cube of the second

Second one

A:4::D:49::F:169
Take the $$n$$th prime where $$n$$ is the position in the alphabet of the letter and square it (i.e, $$A=2^2, B=3^2, C=5^2,\ldots$$)

Third one

439: SQUARE::125:CUBE::216:SQUARE
Take the sum of the digits. If it's a square, then SQUARE. Otherwise, if it's a cube then CUBE. 2+1+6=9 which is a SQUARE.

Fourth one (spotted by @Stiv)

A:8::M:5::J:1::O:10::M:3
Each letter is the first letter of a month with 31 days and the number is its position in the calendar. Since May has appeared already, the next must be March, which is the 3rd month.

• Yes, you are correct on the first three. The last one is tricky though. – Prim3numbah Nov 22 '19 at 11:47
• I suspect rot13(Z jvyy or 3, fvapr gurer ner zbaguf bs gur lrne ortvaavat jvgu nyy bs gurfr yrggref pbeerfcbaqvat gb gurve cbfvgvba va gur lrne va grezf bs zbagu ahzore 1-12. Gur bayl bgure bar ortvaavat jvgu Z vf Znepu va cbfvgvba 3.) Can't spot if there's a particular sub-sequence involved here though... – Stiv Nov 22 '19 at 11:55
• @Stiv Ah I see but you must be right. – hexomino Nov 22 '19 at 11:58