What's this expression mean?

[Guest]

I was watching an old b/w comedy last night and heard this expression: 二三得七

Can someone tell me what it means?

[qrasy]

二 三 得 七
2 (and) 3 get 7

This means 2+3=7, I don't know what it actually means but it should match your context.

[timven1992]

May be she something wrong ,she may said 二三如六
and it is not a plus it is a multiplied and she was talking "九因歌"
You can ask someone who are able to use Chinese Calcalator, They must know them.

一一如一(1x1=1).....一一如九(1x9=9)
二二如四(2x2=4)、二三如六(2x3=6)、二五得一十(2x5=10)......二九一十八(2x9=18 )
三三如九、三四一十二......三八廿四......
四四一十六.........四九三十六......
九九八十一 (The End)

This 九因歌 is inclued in primary school in Hong Kong!
And thats why we no need to remember the product of a multiplied so difficult.