Math  /  Algebra

QuestionLesson 6 Checkpoint EVALUATE
Independent Practice \begin{tabular}{|l|c|c|} \hline Learning Goals & Lesson Reflection (circle one) \\ \hline \begin{tabular}{l} I can determine an explicit expression or steps for \\ calculation from a context \end{tabular} & Starting... Getting There... Got it! \\ \hline \end{tabular} Complete the previous problems, check your solutions, then complete the Lesson Checkpoint below. Complete the Lesson Reflection above by circling your current understanding of the Learning Goal(s).
Write an explicit rule in function notation for the arithmetic sequence.
1. A student loan needs to be paid off beginning the first year after graduation. Beginning at Year 1 , there is $52,000\$ 52,000 remaining to be paid. The graduate makes regular payments of $8,000\$ 8,000 each year. The graph shows the sequence.

A home cook needs to boil 1 liter of water on the stove. Water boils at 100C100^{\circ} \mathrm{C}. \begin{tabular}{|l|c|c|c|} \hline Minutes & 3 & 4 & 5 \\ \hline Temperature (C)\left({ }^{\circ} \mathrm{C}\right) & 38 & 46 & 54 \\ \hline \end{tabular}
2. What is the common difference of the sequence represented in the table?
3. What is the explicit rule for the sequence?
4. Find the temperature at 10 minutes. Is the water boiling yet? lifelong Algebra 1A (2024) Module 3

Studdy Solution

STEP 1

What is this asking? We're figuring out a formula to predict the water temperature at any given time, and then we'll use it to see if the water is boiling after 10 minutes. Watch out! Make sure to check the units – we're dealing with minutes and degrees Celsius.
Also, don't forget that water boils at 100C100^{\circ} \mathrm{C}.

STEP 2

1. Find the common difference.
2. Create the explicit rule.
3. Calculate the temperature at 10 minutes.

STEP 3

Let's look at the change in temperature between the given times.
From 3 minutes to 4 minutes, the temperature increases by 46C38C=8C46^{\circ} \mathrm{C} - 38^{\circ} \mathrm{C} = 8^{\circ} \mathrm{C}.

STEP 4

From 4 minutes to 5 minutes, the temperature increases by 54C46C=8C54^{\circ} \mathrm{C} - 46^{\circ} \mathrm{C} = 8^{\circ} \mathrm{C}.
So, the **common difference** is 8C8^{\circ} \mathrm{C} per minute!

STEP 5

We know the common difference is 8C8^{\circ} \mathrm{C}.
We can represent the temperature at any given minute nn with a formula like this: f(n)=starting temperature+common differencenf(n) = \text{starting temperature} + \text{common difference} \cdot n.
But what's the starting temperature?

STEP 6

We don't know the temperature at 0 minutes, but we *do* know the temperature at 3 minutes is 38C38^{\circ} \mathrm{C}.
If the temperature increases by 8C8^{\circ} \mathrm{C} each minute, then 3 minutes *before* the 3-minute mark (which is 0 minutes), the temperature would have been 38C38C=38C24C=14C38^{\circ} \mathrm{C} - 3 \cdot 8^{\circ} \mathrm{C} = 38^{\circ} \mathrm{C} - 24^{\circ} \mathrm{C} = 14^{\circ} \mathrm{C}.
So our **initial temperature**, f(0)f(0), is 14C14^{\circ} \mathrm{C}!

STEP 7

Now we can write our **explicit rule**: f(n)=14+8nf(n) = 14 + 8n, where nn is the number of minutes and f(n)f(n) is the temperature in degrees Celsius.

STEP 8

Using our awesome formula, we can plug in n=10n = 10 to find the temperature at 10 minutes: f(10)=14+810=14+80=94f(10) = 14 + 8 \cdot 10 = 14 + 80 = 94.

STEP 9

So, after 10 minutes, the water temperature is 94C94^{\circ} \mathrm{C}.
Since water boils at 100C100^{\circ} \mathrm{C}, the water is *not* boiling yet!

STEP 10

The explicit rule for the sequence is f(n)=14+8nf(n) = 14 + 8n.
The temperature at 10 minutes is 94C94^{\circ} \mathrm{C}, which means the water is not boiling yet.

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