I also really like the simple-but-awesome tricks for multiplications: 1) (a + b)(a + c) = a(a + b + c) + bc. Example: 13 14 = 10 * (13 + 4) + 34. You learn t

I also really like the simple-but-awesome tricks for multiplications: 1) (a + b)(a + c) = a(a + b + c) + bc. Example: 13 14 = 10 * (13 + 4) + 34. You learn to "see" 13 14 --> 170 + 12 = 182. 2) (a + b)(xa + c) = a(xa + c + xb) + bc Example: 22 * 62 = 20(62 + 32) + 22 = 1364. Here you would see that 60 = 3 20, so you add 3 * 2 to 62 to get 68, multiply by 20 to get 1360, and then add 2*2. Edit: Er, my stars are turning into italics. You get the idea.