Tanya Sachdeva
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In countries like 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: F:(9/5) C+32

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NCERT Solutions for Class 9 Maths Chapter 4
Important NCERT Questions
Linear equations in two variables
NCERT Books for Session 2022-2023
CBSE Board and UP Board Others state Board
EXERCISE 4.3
Page No:75
Questions No:8

(i) Draw the graph of the linear equation above using Celsius for x-axis and Fahrenheit for y-axis.

(ii) If the temperature is 30°C, what is the temperature in Fahrenheit?

(iii) If the temperature is 95°F, what is the temperature in Celsius?

(iv) If the temperature is 0°C, what is the temperature in Fahrenheit and if the temperature is 0°F, what is the temperature in Celsius?

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

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2 Answers

  1. Get Hindi Medium and English Medium NCERT Solution for Class 9 Maths to download.
    Please follow the link to visit website for first and second term exams solutions.
    https://www.tiwariacademy.com/ncert-solutions/class-9/maths/chapter-4/

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  2. (i) Taking Celsius on x-axis and Fahrenheit on y-axis, the linear equation is given by: y = (9/5)x + 32
    For plotting the graph:
    Putting x = 0, we have, y = (9/5) × 0 + 32 = 32
    putting x = 5, we have, y = (9/5) × 5 + 32 = 41
    Putting x = 10, we have, y = (9/5) × 10 + 32 = 50
    Hence, A(0, 100), B(5, 41) and c(10, 50) are the solutions of the equation.

    (ii) If the temperature is 30° C, then
    F = (9/5) × 30 + 32 = 54 + 32 = 86
    Hence, if the temperature is 30°C, the temperature in Fahrenheit is 86°F.

    (iii) If the temperature is 95°F, then
    95 = (9/5)C + 32
    ⇒ 95 – 32 = (9/5)C
    ⇒ 63 × 5/9 = C
    ⇒ C = 35°
    If the temperature is 95°F, the temperature in Celsius is 35°C.

    (iv) If temperature is 0°C, then
    F = (9/5) × 0 + 32 = 0 + 32 = 32
    If the temperature is 0°F, then
    0 = (9/5)C + 32
    ⇒ -32 = (9/5)C
    ⇒ -32 × 5/9 = C
    ⇒ – 160/9 = C
    ⇒ C = -17.8°
    If the temperature is 0°C, the temperature in Fahrenheit is 32°F and if the temperature is 0°F, the temperature in Celsius is -17.8°C.

    (v) Let x° be the temperature which is numerically the same in both Fahrenheit and Celsius, then
    x = (9/5)x + 32
    ⇒ x – 32 = (9/5)x
    ⇒ (x – 32) × 5 = 9x
    ⇒ 5x – 160 = 9x
    ⇒ 4x = -160
    ⇒ x – 40°
    Hence, -40° is the temperature which is numerically the same in both Fahrenheit and Celsius.

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