In which model does the shaded portion represent 70%?

the answer is 11.2 (i know i’m late)

the awnser is 10,000 times greater than 5.39×10^−2

the cross section of an object is the shape you get when you cut straight through an object.

thus the cross section of the human hair is a circle. hence the cross sectional area is the area of a circle and area of circle is :

a = 3.14 × r²

we are given that the average width of human hair is = 4 × (1 / 10³) cm.

so the diameter of the circle is = 4 × (1 / 10³) cm.

∴ radius r = (diameter/2) = 2 × (1/10³) cm

now area a = 3.14 × (2 × (1/10³))² cm²

scientific notation is a standard way of writing very large and very small numbers so that they’re easier to both compare and use in computations. to write in scientific notation, follow the form

n × 10 ᵃ

where n is a number between 1 and 10, but not 10 itself, and a is an integer (positive or negative number).

so area can be rewritten in scientific notation as :

⇒ 3.14 × 4 × (1/10⁶)

⇒ 12.56 × 10 ⁻⁶ cm²

⇒1.256 × 10⁻⁷ cm²