Question 127224
If cubic feet of gas is plotted on the horizontal axis
and the corresponding cost on the vertical axis,
we are given 2 points, (1000, 39) and (3000,99)
There is a formula you can use
{{{(y[2] - y[1]) / (x[2] - x[1]) = (y - y[1]) / (x - x[1])}}}
the given points are (x[2],y[2]) and (x[1],y[1])
{{{(99 - 39) / (3000 - 1000) = (y - 39) / (x - 1000)}}}
{{{60 / 2000 = (y - 39) / (x - 1000)}}}
{{{3/100 = (y - 39) / (x - 1000)}}}
multiply both sides by {{{100*(x - 1000)}}}
{{{3*(x - 1000) = (y - 39)*100}}}
{{{3x - 3000 = 100y - 3900}}}
{{{100y = 3x + 900}}}
{{{y = (3/100)x + 9}}} or in this case,
{{{C = (3/100)n + 9}}} answer
check:
See if this line goes through (1000, 39) and (3000,99)
{{{C = (3/100)n + 9}}}
{{{39 = (3/100)*1000 + 9}}}
{{{39 = 30 + 9}}}
{{{39 = 39}}}
OK
{{{C = (3/100)n + 9}}}
{{{99 = (3/100)3000 + 9}}}
{{{99 = 90 + 9}}}
{{{99 = 99}}}
OK
Find the cost of 2400 cubic feet of natural gas.
{{{C = (3/100)n + 9}}}
{{{C = (3/100)2400 + 9}}}
{{{C = 72 + 9}}}
{{{C = 81}}} dollars answer