Question 515003
Let {{{B}}} = number of boxes
Let {{{P}}} = price charged
Assume a straight line
The data given tells what the slope of the line is.
Plot {{{P}}} on the vertical axis
Plot {{{B}}} on the horizontal axis
slope = {{{ (4 - 3) / ( 120 - 250 ) }}}
slope = {{{ -1/130 }}}
The equation so far is:
{{{ P = -1/130*B + P[0] }}}
Where {{{ P[0] }}} is the vertical intercept
Plugging in data:
{{{ -1/130 = -.0077 }}}
{{{ 3 = -1/130*250 + P[0] }}}
{{{ P[0] = 3 + 1.923 }}}
{{{ P[0] = 4.923 }}}
The equation is:
{{{ P = -.0077B + 4.923 }}}
check answer:
{{{ 4 = -.0077*120 + 4.923 }}}
{{{ 4 = -.924 + 4.923 }}}
{{{ 4 = 3.999 }}} ( error due to rounding off)
and
{{{ 3 = -.0077*250 + 4.923 }}}
{{{ 3 = -1.925 + 4.923 }}}
{{{ 3 = 2.998 }}} ( also round-off error )
Here's the plot:
 {{{ graph( 400, 400, -50, 700, -1, 6, -.0077x + 4.923 ) }}}