Multiply by 12
Multiply by 10, then add double the original.
34 × 12 = 408
Twelve 34s is ten of them plus two of them.
The two of them is a double: 34 × 2 = 68.
Add the parts: 340 + 68 = 408.
Your turn
Three to try in your head — tap what you get.
29 × 12
96 × 12
73 × 12
All 36 shortcuts: the Magic Tricks library.