20 % or 0.2 portion of his screws he will need to use.
According to the question
A builder has 8 boxes of screws in his storage.
Each box contains 400 screws.
So, 8 × 400
= 3200 screw in 8 boxes
If he needs 640 to complete a project, what portion of his screws he will need to use:
= [tex]\frac{640}{3200} \times 100[/tex]
= (1/5) × 100
= 20 % or 0.2
Therefore,
20 % or 0.2 portion of his screws he will need to use.
Find out more information about portion here
https://brainly.com/question/11259177
#SPJ4