Question 1109525
You are given a point and the slope
for both MW and W populations
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For MW:
( 0, 60 )
{{{ m = .4 }}}
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For W:
( 0, 53 )
{{{ m = 1 }}}
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Time in yrs is plotted on the horizontal axis as {{{ t }}}
Population in millions is plotted on the vertical axis as {{{ P }}}
The given points are vertical axis intercepts.
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For MW:
{{{ P = .4t + b }}}
{{{ 60 = .4*0 + b }}}
{{{ b = 60 }}}
{{{ P = .4t + 60 }}}
For W:
{{{ P = 1*t + b }}}
{{{ 53 = 1*0 + b }}}
{{{ b = 53 }}}
{{{ P = t + 53 }}}
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Set the populations, {{{ P }}}
equal to eachother
{{{ .4t + 60 = t + 53 }}}
{{{ .6t = 7 }}} 
{{{ t = 11.667 }}}
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The populations will be the same in 
1990 + 11.667 yrs = 2001 and 8 months
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check:
{{{ P = .4*11.667 + 60 }}}
{{{ P = 64.667 }}}
and
{{{ P = 11.667 + 53 }}}
{{{ P = 64.667 }}}
OK