# Replace the question marks with one single word

This one needs a lot of lateral thinking

In the equation below replace all the question marks with one single word (same word at every question mark).

Then show that the equation is correct.

• Frankly, NaN (not a number) busts this whole thing wiiiiide open – Avi Nov 4 '19 at 14:34
• Is it an equation (condition) formulated in some programming language? – z100 Nov 4 '19 at 20:11
• No @z100. Kind of straightforward – DrD Nov 4 '19 at 21:33

Use ?=ROT to get:

ROT(ROT5(68))[ROT5(105)]=ROT(ROT5(68))[P]/ROT(ROT5(68))[Q]

which becomes:

ROT13[ROT5(105)]=ROT13[P]/ROT13[Q]

Now the clever bit, 105=CV in Roman numerals, and P->C, Q->D in ROT13:

ROT13(CV)=C/D

PI=Circumference/Diameter