Name:
5. The function $Q=0.003 t^{2}-0.625 t+25$ represents the amount of energy, in Joules, in a battery after t minutes of use.
a) State the amount of energy held by the battery immediately before it was used. [1]
\[
\begin{aligned}
Q & =0.003 t^{2}-0.625 t+25 \\
& =0.003(0)^{2}-0.625(0)+25 \\
Q & =25
\end{aligned}
\]
b) Calculate the number of minutes it takes for the energy to reach zero. [4]

Answer

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Answer

$\boxed{\text{b) 53.99 minutes}}$

Steps

Step 1 ：$Q = 0.003 t^{2} - 0.625 t + 25$

Step 2 ：$Q = 0.003(0)^{2} - 0.625(0) + 25$

Step 3 ：$Q = 25$

Step 4 ：$0 = 0.003t^2 - 0.625t + 25$

Step 5 ：$t \approx 53.99$

Step 6 ：$\boxed{\text{a) 25 Joules}}$

Step 7 ：$\boxed{\text{b) 53.99 minutes}}$