exact vs. exactly

[English Learner]

English Grammar Error, Intermediate level

ESL/EFL Test #4 "When you go to France...", question 2

I can't tell you the exactly number but I think it's probably fourteen.

(a) tell
(b) exactly
(c) but
(d) probably

English Grammar Error, Intermediate level

ESL/EFL Test #4 "When you go to France...", answer 2

I can't tell you the exact number but I think it's probably fourteen.

Correct entry: exact
The error was: (b) exactly
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why

English Learnerrrrr

[Mister Micawber]

.
The original sentence contains the adverb, 'exactly', but what is required is an adjective ('exact') to modify the noun, 'number'.
.
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Native English teacher at Mister Micawber's

[Chaaki]

" exact" is an adjective so, it is normal to describe a noun . But "exactly" is an adverb and it describe an action" how "