so, notice, the slope of that equation is just -4/5, and any parallel line to it will have the same exact slope.
so we're really looking for the equation of a line whose slope is -4/5 and runs through x-intercept of 3, namely (3,0).
We will assume that he does not replace the first one.
He needs to choose 2 good one from 16 good ones. How can he do this?
The total number of ways of choosing 2 lightbulbs [good or bad] is
So the probability of getting a good light bulb is
The surface area formula for a cube is: 6 * s^2, where s is the side length.
The two surface areas are:
6 * 3^2 = 54
and
6 * 8^2 = 384
The ratio of their surface areas, from the surface area of the smaller cube to the surface area of the larger cube is:
54/384 = 9/64
The answer is 9/64.
Note that another way to to find the ratio of the squares of the side lengths of the cubes.
64/3.2 = 20
The answer is 20
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