Tonight while playing Phase 10 with the fam, we ended up talking about how I calculate multiplcation tables, in particular, my methods for finding the 5 and 9′s.
For the 5′s (5 * X = Y).
- Y = (X/2)*10
- X = 7
- Y = (7/2)*10
- Y = 3.5 * 10
- Y = 35
For the 9′s (9 * X = Y) it’s a little different since I do string concatenation. To do this in the equation, I’ll be using & to combine the numbers (i.e. 1 & 2 = 12).
- Y = X-1 & (9-(X-1))
- X = 4
- Y = 4-1 & (9-(4-1))
- Y = 3 & 6
- Y = 36
