Question 971766
 Every two years the value of a $225 investment at CIBC grows by $50.
 At RBC, a $150 investment grows by $90 every 3 years.
 Use a graphical method to determine when the investments are worth the same value.
:
Assume the 1st investments will grows $25 a yr, the 2nd investment by $30 a yr
:
Let x = no. of yrs invested
let y = accumulated value of the investments
:
Write an equation for each
y = 25x + 225
and
y = 30x + 150
:
plot these two equations
{{{ graph( 300, 200, -6, 25, -100, 1000, 25x+225, 30x+150) }}}
Looks like they intersect at x = 15, y looks like $600
:
you can confirm the point of intersection using the equations
30x + 150 = 25x + 225
30x - 25x = 225 - 150
5x = 75
x = 75/5
x = 15 yrs they will be equal
:
Their value then
y = 25(15) + 225
y = $600
the same with the other equation
y = 30(15) + 150
y = $600