Questions: In this example we considered the function W=f(T, v), where W is the wind-chill index, T is the actual temperature, and v is the wind speed. A numerical representation is given in this table. (a) What is the value of f(-15,60) ? What is its meaning? We get f(-15,60)= , which means that if the temperature is -15°C and the wind speed is 60 km / h, then the air would feel equivalent to approximately °C without wind. (b) Describe in words the meaning of the question "For what value of v is f(-20, v)=-30 ?" The question is asking: when the temperature is °C, what wind speed gives a wind-chill index of °C ? Answer the question. v= km / h (c) Describe in words the meaning of the question "For what value of T is f(T, 20)=-43 ?" The question is asking: when the wind speed is km / h, what temperature gives a wind-chill Index of °C ? Answer the question. T= °C (d) What is the meaning of the function W=f(-10, v) ? Describe the behavior of this function. The function W=f(-10, v) means that we fix T at and allow v to vary, resulting in a function of one variable. In other words, the function gives wind-chill index values for different wind speeds when the temperature is °C. From the table (look at the row corresponding to T=-10 ), the function - Select - and appears to approach a constant value as v increases. (e) What is the meaning of the function W=f(T, 80) ? Describe the behavior of this function. The function W=f(T, 80) means that we fix v at and allow T to vary, again giving a function of one variable. In other words, the function gives wind-chill index values for different temperatures when the wind speed is km / h. From the table (look at the column corresponding to v=80 ), the function -Select - almost linearly as T Increases.

In this example we considered the function W=f(T, v), where W is the wind-chill index, T is the actual temperature, and v is the wind speed. A numerical representation is given in this table.
(a) What is the value of f(-15,60) ? What is its meaning?

We get f(-15,60)= , which means that if the temperature is -15°C and the wind speed is 60 km / h, then the air would feel equivalent to approximately  °C without wind.
(b) Describe in words the meaning of the question "For what value of v is f(-20, v)=-30 ?"

The question is asking: when the temperature is  °C, what wind speed gives a wind-chill index of  °C ?

Answer the question.
v=  km / h
(c) Describe in words the meaning of the question "For what value of T is f(T, 20)=-43 ?"

The question is asking: when the wind speed is  km / h, what temperature gives a wind-chill Index of  °C ?

Answer the question.
T=  °C
(d) What is the meaning of the function W=f(-10, v) ? Describe the behavior of this function.

The function W=f(-10, v) means that we fix T at  and allow v to vary, resulting in a function of one variable. In other words, the function gives wind-chill index values for different wind speeds when the temperature is   °C. From the table (look at the row corresponding to T=-10 ), the function - Select - and appears to approach a constant value as v increases.
(e) What is the meaning of the function W=f(T, 80) ? Describe the behavior of this function.

The function W=f(T, 80) means that we fix v at  and allow T to vary, again giving a function of one variable. In other words, the function gives wind-chill index values for different temperatures when the wind speed is  km / h. From the table (look at the column corresponding to v=80 ), the function -Select - almost linearly as T Increases.
Transcript text: In this example we considered the function $W=f(T, v)$, where $W$ is the wind-chill index, $T$ is the actual temperature, and $v$ is the wind speed. A numerical representation is given in this table. (a) What is the value of $f(-15,60)$ ? What is its meaning? We get $f(-15,60)=$ $\square$ , which means that if the temperature is $-15^{\circ} \mathrm{C}$ and the wind speed is $60 \mathrm{~km} / \mathrm{h}$, then the air would feel equivalent to approximately $\square$ ${ }^{\circ} \mathrm{C}$ without wind. (b) Describe in words the meaning of the question "For what value of $v$ is $f(-20, v)=-30$ ?" The question is asking: when the temperature is $\square$ ${ }^{\circ} \mathrm{C}$, what wind speed gives a wind-chill index of $\square$ ${ }^{\circ} \mathrm{C}$ ? Answer the question. $v=$ $\square$ $\mathrm{km} / \mathrm{h}$ (c) Describe in words the meaning of the question "For what value of $T$ is $f(T, 20)=-43$ ?" The question is asking: when the wind speed is $\square$ $\mathrm{km} / \mathrm{h}$, what temperature gives a wind-chill Index of $\square$ ${ }^{\circ} \mathrm{C}$ ? Answer the question. $T=$ $\square$ ${ }^{\circ} \mathrm{C}$ (d) What is the meaning of the function $W=f(-10, v)$ ? Describe the behavior of this function. The function $W=f(-10, v)$ means that we fix $T$ at $\square$ and allow $v$ to vary, resulting in a function of one variable. In other words, the function gives wind-chill index values for different wind speeds when the temperature is $\qquad$ ${ }^{\circ} \mathrm{C}$. From the table (look at the row corresponding to $T=-10$ ), the function - Select $-\checkmark$ and appears to approach a constant value as $v$ increases. (e) What is the meaning of the function $W=f(T, 80)$ ? Describe the behavior of this function. The function $W=f(T, 80)$ means that we fix $v$ at $\square$ and allow $T$ to vary, again giving a function of one variable. In other words, the function gives wind-chill index values for different temperatures when the wind speed is $\square$ $\mathrm{km} / \mathrm{h}$. From the table (look at the column corresponding to $v=80$ ), the function -Select $-v$ almost linearly as $T$ Increases.
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Solution

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Solution Steps

Solution Approach

(a) To find the value of f(15,60) f(-15, 60) , we need to look up the value in the given table where the temperature T T is 15-15 and the wind speed v v is 6060. This value represents the wind-chill index, which indicates how cold it feels at that temperature and wind speed.

(b) The question asks for the wind speed v v that results in a wind-chill index of 30-30 when the temperature is 20-20. We need to find the value of v v in the table where f(20,v)=30 f(-20, v) = -30 .

(c) The question asks for the temperature T T that results in a wind-chill index of 43-43 when the wind speed is 2020. We need to find the value of T T in the table where f(T,20)=43 f(T, 20) = -43 .

Step 1: Determine f(15,60) f(-15, 60)

To find the value of f(15,60) f(-15, 60) , we look up the table where the temperature T=15 T = -15 and the wind speed v=60 v = 60 . The table provides the wind-chill index for these conditions.

Step 2: Interpret the Meaning of f(15,60) f(-15, 60)

The value f(15,60)=30 f(-15, 60) = -30 means that when the actual temperature is 15C-15^\circ \mathrm{C} and the wind speed is 60km/h60 \, \mathrm{km/h}, the air feels like 30C-30^\circ \mathrm{C} without wind.

Step 3: Find v v for f(20,v)=30 f(-20, v) = -30

We need to find the wind speed v v such that f(20,v)=30 f(-20, v) = -30 . From the table, when T=20 T = -20 , the wind speed v=60 v = 60 results in a wind-chill index of 30-30.

Step 4: Interpret the Meaning of f(20,v)=30 f(-20, v) = -30

This means that when the temperature is 20C-20^\circ \mathrm{C}, a wind speed of 60km/h60 \, \mathrm{km/h} makes the air feel like 30C-30^\circ \mathrm{C}.

Step 5: Find T T for f(T,20)=43 f(T, 20) = -43

We need to find the temperature T T such that f(T,20)=43 f(T, 20) = -43 . However, the table does not provide a value for T T that satisfies this condition, as indicated by the result T=None T = \text{None} .

Final Answer

  • f(15,60)=30 f(-15, 60) = \boxed{-30}
  • v v for f(20,v)=30 f(-20, v) = -30 is 60km/h\boxed{60 \, \mathrm{km/h}}
  • T T for f(T,20)=43 f(T, 20) = -43 is None\boxed{\text{None}} (no such temperature exists in the table)
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