# Open the third door!

I was wandering in an abandoned house. When I went down to the basement I found three doors. All three doors have a triangle painted on them, two of them with a number outside the triangle, these doors could open. Now I would like to open the third door to see what it conceals, therefore the missing number must be found. • Wait, why the first door has 5 numbers? Apr 6, 2020 at 8:57
• @CulverKwan Presumably figuring that out is part of the puzzle. Apr 6, 2020 at 9:23
• Honestly, if I'm wandering in an abandoned house and I see some cryptic numbers and a door that doesn't open, I'm probably just leaving before the creepy soundtrack with a single piano key plink starts. Apr 6, 2020 at 15:48
• rot13(Abg fher vs vz ba gur evtug genpx.. Vf gur nafjre n zhygvcyr bs 4?) Apr 7, 2020 at 7:41
• @Prim3numbah Nope
– tyui
Apr 7, 2020 at 7:44

15

If we look at the numbers in the 1st triangle

96 represents 9*6=54, 83 represents 8*3=24, 20 represents 2*0=0, 12 represents 1*2=2. Now, if we add these numbers together we get 54+24+0+2=80. The number outside the traingle are the average of the 4 numbers, which is 80/4=20.

The 2nd triangle

The same logic goes here. 117 represents 7, 93 represents 27, 21 represents 2. The total sum is 36. And this time we have 3 numbers inside the triangle so the average is 36/3=12.

Lastly the 3rd triangle(equivalent to 2nd triangle)

218 represent 16, 53 represents 15 and 27 represents 14. So the average is therefore 45/3=15.