- Dear Teachers,

1. I'm doing the washing-up.

2. I'm washing the dishes.

3. I'm doing the dishes.

- Are these the same meaning?

Thanks very much to Teachers,

I think #1 is moreBritish; #2 and #3 are more common in the U.S.
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You could also say 'I'm washing up'.

However, I think that, in USA English, this can mean 'I'm washing my hands and face.'

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In AmE, You wash up when you wash your face and hands.
In BrE, You wash up when you wash the dishes and cutlery that have been used for a meal.