三下五除二

Chinese

Etymology

Step 1	Step 2	Step 3
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A mnemonic device to aid with adding 3 to 2, 3 and 4 in base 10 (also 7, 8 and 9 in base 16) on an abacus.

For example, to calculate $3+3$:

1. Start with three beads on the bottom (each lower bead is equal to 1).
2. Move one of the top beads down (each top bead is equal to 5).
3. Take away two of the beads from the bottom.
4. This leaves you with one top bead (5) and one bottom bead (1), for a total of 6.

Idiom

1. Template:Lb (doing things) in an instant; in the blink of an eye; quickly and easily
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