# NCERT Class 9 Solutions: Linear Equation in Two Variable (Chapter 4) Exercise 4.3 – Part 5 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q-8 In countries like the USA and Canada, temperature is measured in Fahrenheit, whereas in countries like India, it is measured in Celsius. Here is a linear equation that converts Fahrenheit to Celsius.

- Draw the graph of the linear equation above using Celsius for and Fahrenheit for
- If the temperature is , what is the temperature in Fahrenheit?
- If the temperature is , what is the temperature in Celsius?
- If the temperature is , what is the temperature in Fahrenheit and if the temperature is , what is the temperature in Celsius?
- Is there a temperature which is numerically the same in both Fahrenheit and Celsius? If yes, find it.

Solution:

Given equation is

- Draw the graph of the linear equation above using Celsius for and Fahrenheit for

Let temperature in Celsius be and Fahrenheit be

So the equation will be . Note how this equation expresses temperature in Fahrenheit for a given temperature in Celsius.

To graph this equation we find a few points:

- Putting the value of in equation (1)

Or ,

So the point is

- Putting the value in equation (1)

Or,

So, point is

- Putting the value in equation (1)

Or,

So, solution is

Therefore graph becomes

- If the temperature is , what is the temperature in Fahrenheit?

If,

- If the temperature is , what is the temperature in Celsius?

So,

Or

Or

Or

- If the temperature is , what is the temperature in Fahrenheit and if the temperature is , what is the temperature in Celsius?
- When ,
- When ,

So, required temperature

- Is there a temperature which is numerically the same in both Fahrenheit and Celsius? If yes, find it.

Let the same temperature be numerically. This temperature *m* in Fahrenheit should be same as temperature *m* in Celsius, i.e.. = . We know that . Therefore,

let՚s solve this equation,

So, numerical value of required temperature