Question

Question 11 A solution is to be kept between 68°F and 77°F. What is the range in temperature in degree Celsius (C) if the Celsius/Fahrenheit (F) conversion formula is given by F = 9C/8 + 32

Class X1 - Maths -Linear Inequalities Page 132

Answer 1

Let F is the temperature in Fahrenheit .
a/c to question,
68°F ≤ F ≤ 77°F

but we know,
F = 9C/5 + 32 , use this here,

68≤ 9C/5 + 32 ≤ 77

68 -32≤ 9C/5 ≤ 77 -32

36 ≤ 9C/5 ≤ 45

multiply 8/9 in all sides,

36 × 5/9 ≤ 9C/5 × 5/9 ≤ 45 × 5/9

20 ≤ C ≤ 25

hence, range of temperature in degree between 20°C to 25°C

Answer 2

Let F is the temperature in Fahrenheit .

a/c to question,

68°F ≤ F ≤ 77°F

but we know,

F = 9C/5 + 32 , use this here,

68≤ 9C/5 + 32 ≤ 77

68 -32≤ 9C/5 ≤ 77 -32

36 ≤ 9C/5 ≤ 45

multiply 8/9 in all sides,

36 × 5/9 ≤ 9C/5 × 5/9 ≤ 45 × 5/9

20 ≤ C ≤ 25

hence, range of temperature in degree between 20°C to 25°C