Welcome to the magic show. First the magician is blindfolded. Now the assistant asks 4 members of the audience to write 4 distinct numbers between 1 and 9 (inclusive) on the back of 4 cards. The numbers are shown to the assistant and the audience. Now the audience is asked to hide one of the card...

1^2=1 1*2=2 1+2=3 rounddown(1/.2~)=4 or roundup(squareroot(12)) 1/.2=5 (1+2)!=6 d/dx(1)+rounddown(e^2)=7 roundup(1π)+roundup((!2)π)=8 rounddown(1π)+rounddown(2π)=9 rounddown(1π)+roundup(2π)=10

There's a riddle given by my friend to me. The answer is one real word from this list:https://github.com/bitcoin/bips/blob/master/bip-0039/english.txt The riddle word can be find by solving 3 riddles. I think the common property between these 3 is the answer but I am not sure. Here are 3 words fr...

If 9 x 17 = 49, 13 x 31 = 100, 12 x 18 = 81 then find 14 x 4 =? 1)100 2)81 3)64 4)121

So recently I was scrolling through Youtube when I came across this video from MindYourDecisions that was about solving a legendary math puzzle. The puzzle: Place the numbers 1 through 9 in the following boxes such that ☐☐ x☐ --- ☐☐ +☐☐ --- ☐☐ Each number can only be used once. Here is t...

Suppose we have a function such that$$f(f(x))=2x+4\quad\forall x\in\mathbb R$$Does such a function $f:\mathbb R\to\mathbb R$ exist that satisfies the relation, or does such a function not exist?

My business is going quite well, and I finally make the decision to train up an apprentice, as the workload has been only getting worse lately. Luck clearly is on my side - I put up the ad yesterday, and already today there's a person at my doorstep asking about the apprenticeship! I am a bit des...