Same result

[mindinka]

Hi guys there is something interesting found on Internet anyone could explain that..?
Pick a number from 1-9.
Multiply by 3.
Add 3.
Multiply by 3 again.
Now add the two digits together and the result is always 9, isn't it?

 

[Dwarf]

OK. Let A represent the initial number and B & C the intermediates.

We have A x 3 = B, B + 3 = C and C x 3 = A [9-A]

The final result is always a 2 digit number with the first digit being the original number and the second being 9 minus that number.

Here's some more interesting reading: Casting out nines - Wikipedia, the free encyclopedia

 

[Everlong]

I remember doing this when I was in, I think my second year, of primary school. We had this as a maths problem, and the teacher chose a few numbers between 1 and 9 for us to work out and obviously the answer was always going to be 9, but I didn't understand it when I was only 6 years old. I thought I was doing it wrong because it didn't make sense to be getting the same answer for 3 questions in a row, lol.

 

[mindinka]

I missed that lesson... I guess...