The correct answer is option A which is the conversion ratio will be 1 Hour = 60 Minutes.
Multiplication or division by a numerical factor, selection of the correct number of significant figures, and unit conversion are all steps in a multi-step procedure.
Given that:-
The conversion ratio will be given as:-
1 Hour = 60 Minutes
9 hours = 9 x 60 = 540 minutes.
So he read the book for 540 minutes.
Therefore the correct answer is option A which is the conversion ratio will be 1 Hour = 60 Minutes.
To know more about unit conversion follow
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