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Let y vary directly as x. If y = 12 when x = 4, then write a linear equation. What is the value of y when x = 5

Solution:

Given, y varies directly as x.

Also, y = 12 when x = 4.

We have to write a linear equation and find the value of y when x = 5.

As y varies directly as x, y ∝ x

Therefore, the linear equation is y = kx

Where k is an arbitrary constant

From the given point,

12 = k(4)

k = 12/4

k = 3

Therefore, the linear equation is y = 3x

Put x = 5 in the equation,

y = 3(5)

y = 15

Therefore, the value of y is 15.

✦ Try This: Let y vary directly as x. If y = 10 when x = 5, then write a linear equation. What is the value of y when x = 3?

☛ Also Check: NCERT Solutions for Class 9 Maths Chapter 4

NCERT Exemplar Class 9 Maths Exercise 4.3 Problem 10

Let y vary directly as x. If y = 12 when x = 4, then write a linear equation. What is the value of y when x = 5

Summary:

A linear equation is an equation in which the highest power of the variable is always one. Let y vary directly as x. If y = 12 when x = 4, then the linear equation is y = 3x. The value of y when x = 5 is 15

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