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A speck of dust in an electron microscope is 1.2x10^2 millimeters wide. The image is 5x10^2 times larger than the actual size. How many millimeters wide is the actual speck of dust?

Verified Answer :

nobillionaireNobley

Let the actual size be x, then
(5 x 10^2)x = 1.2 x 10^2
x = (1.2 x 10^2 / 5 x 10^2) = 0.24 millimeters

Therefore, the actual size is 0.24 millimiters.

Lampa20

let d be the width of dust seen in electron microscope.
d = 1.2 10^2 mm

let x be the scaling parameter.
x = 510^2mm

dusts actual width D is calculated by scaling d by a factor of x

D = d/x
D =  0.24mm

Note that you are scaling dimensions by a factor of x and not surface of the dust.

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