Question #84641

1 Answer
Apr 2, 2017

6 hours

Explanation:

color(blue)("Using visual assessment")

Notice that the line intercepts the bottom axis at 9 and also the side axis at 9.

This condition is means that the value you select for one axis relates to the same value on the other axis.

Thus 3 hours watching TV relates to 6 hours sleeping.

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color(blue)("Using mathematical assessment")

One of the standardised forms for the equation of a strait line is:

y=mx+c

where m is the slope (gradient) and c is the y-intercept.

By observation the y-intercept is 9 ->y=mx+9

m is the slope (gradient) reading left to right on the bottom axis

m->("change in sleeping")/("change in TV") -> (0-9)/(9-0) =-1

So we now have: y=(-1)x+9" "->" "y=-x+9

We need the value of y when sleep is 3 hours

y=-x+9" "->" "y=-3+9=6

Tony BTony B