'surprised at how many' instead of 'surprised how many'

[Ljiljan Maksimovich]

English Grammar Tests, Elementary Level

ESL/EFL Test #90 "Using Make and Do (1)", question 1

The manager was surprised at how many things Ron could ......... at once.

(a) make
(b) do
(c) made
(d) did

English Grammar Tests, Elementary Level

ESL/EFL Test #90 "Using Make and Do (1)", answer 1

The manager was surprised at how many things Ron could do at once.

Correct answer: (b) do

Your answer was: correct
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Why should we use "surprised at how many..." instead of "surprised how many..."?

Thanks
Ljiljan

[Alan]

Hi Ljiljan,

Both surprised how and surprised at how are acceptable.

Alan
_________________
English as a Second Language
You can read my ESL story Present Simple

[Mickhael]

Hello everyone,

What does 'do' mean in this context? Thank you for your help.

[Alan]

Hi,

'Do' in this context suggests 'perform or 'manage to achieve'.

Alan
_________________
English as a Foreign Language
You can read my EFL story Progressive Forms