let the number = x
x*80/100 = 55
x = 5500/80
x=68.75
After rounding off, it will remain 68.75
x-coordinates for the maximum points in any function f(x) by f'(x) =0 would be x = π/2 and x= 3π/2.
<h3>How to obtain the maximum value of a function?</h3>
To find the maximum of a continuous and twice differentiable function f(x), we can firstly differentiate it with respect to x and equating it to 0 will give us critical points.
we want to find x-coordinates for the maximum points in any function f(x) by f'(x) =0
Given f(x)= 4cos(2x -π)

In general 
from x = 0 to x = 2π :
when k =0 then x = π/2
when k =1 then x= π
when k =2 then x= 3π/2
when k =3 then x=2π
Thus, X-coordinates of maximum points are x = π/2 and x= 3π/2
Learn more about maximum of a function here:
brainly.com/question/13333267
#SPJ4
"77.25 in²" ..............
Answer:
D 6
Step-by-step explanation:
1-2=-1 and the absolut value of -1 is 1
2--3=5
5+1=6