SOLUTION: A plant whose height is 8 cm, is growing at a rate of 4/5 cm per week. When will its height exceed 13 3/5 cm? Thank you

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Question 152269: A plant whose height is 8 cm, is growing at a rate of 4/5 cm per week. When will its height exceed 13 3/5 cm?
Thank you
Found 2 solutions by jim_thompson5910, ankor@dixie-net.com:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
The starting height is 8 cm, so this means that the constant of the equation y=mx%2Bb is 8. This means that b=8. Since it "is growing at a rate of 4/5 cm per week", the slope is m=4%2F5. So the entire equation is

y=%284%2F5%29x%2B8


Now convert 13%263%2F5 to an improper fraction


13%263%2F5=%2813%2A5%2B3%29%2F5=%2865%2B3%29%2F5=68%2F5


y=%284%2F5%29x%2B8 Start with the given equation.


68%2F5=%284%2F5%29x%2B8 Plug in y=68%2F5. This is the same as y=13%263%2F5


68%2F5-8=%284%2F5%29x Subtract 8 from both sides.


28%2F5=%284%2F5%29x Combine like terms


7=x Multiply both sides by 5%2F4 to isolate x.


So the answer is x=7 which means that it will take 7 weeks for the plant to reach (and exceed) a height of 13%263%2F5 cm.

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A plant whose height is 8 cm, is growing at a rate of 4/5 cm per week. When will its height exceed 13 3/5 cm?
:
Let t = time required to do this;
:
Use decimals here:
.8t + 8 > 13.6
.8t > 13.6 - 8
.8t > 5.6
t > 5.6%2F.8
t > 7 weeks