Processing math: 100%

Subscribe to our YouTube channel for the latest videos, updates, and tips.


Change of Subject of Formula

In previous topic of this chapter we have learnt about the subject in a formula. We know that a formula has both known and unknown quantities in it and the unknown quantity that we need to find using the hints and values of known quantities in the given question is said to be the subject of the formula. 

Under this topic we will learn to change the subject of the formula. A formula can be given in any form but to change the subject we have to identify the known and unknown quantities given in the question. In some cases, the formula we know can directly be applied in order to get the value of the unknown quantity but in some cases we need to change the subject of the formula and then find the unknown quantity using the hints and known values. To change the subject of the formula, all we need to apply are simple mathematical operators such as addition, subtraction, division and multiplication. 

Let us take an example to understand the concept in a better way.

1. We all know the following newton’s equation of motion;

 v = u + at

               where v = final velocity of the particle

                         u = initial velocity of the particle 

                         a = acceleration of the particle

                         t = time taken by the particle to accelerate

here final velocity of the particle, i.e., is the subject of the formula.

Suppose we want to change the subject to ‘t’, then:

Step I: subtract ‘u’ from both sides of the equation.

    v – u = u + at – u

⟹ v – u = at


Step II: Divide both sides of the equation by ‘a’:

vua = at/t

vua = t


Above equation is the required equation in which the subject is ‘t’.

In this way subject of an equation can be changed from one form to another.


Let’s have a look on another example of changing subject of formula:

2. considering another equation of newton’s equation of motion:

s = ut + ½ at2

where   s = displacement of the particle

            u = initial velocity of the particle

            a = acceleration of the particle

            t = time taken by the particle to cover the displacement.

In this equation, the displacement of the particle ‘s’ is the subject of the formula.


Now, if we want to change the subject of the formula from ‘s’ to ‘u’, one should the following steps:

Step I: Subtracting ½ at2 from both sides of the equation, we get

          s – ½ at2 = ut


Step II: dividing both sides of the equation by ‘t’, we get

s12at2t = ut/t

⟹ s/t – ½ at = u

hence the above equation is the equation having ‘u’ as the subject of the formula.


Similarly, subject of the formula can be changed by using simple mathematical operations.




9th Grade Math

From Change of Subject of Formula to HOME PAGE




Didn't find what you were looking for? Or want to know more information about Math Only Math. Use this Google Search to find what you need.



New! Comments

Have your say about what you just read! Leave me a comment in the box below. Ask a Question or Answer a Question.




Share this page: What’s this?

Recent Articles

  1. 8 Times Table | Multiplication Table of 8 | Read Eight Times Table

    May 18, 25 04:33 PM

    Printable eight times table
    In 8 times table we will memorize the multiplication table. Printable multiplication table is also available for the homeschoolers. 8 × 0 = 0 8 × 1 = 8 8 × 2 = 16 8 × 3 = 24 8 × 4 = 32 8 × 5 = 40

    Read More

  2. Worksheet on Average | Word Problem on Average | Questions on Average

    May 17, 25 05:37 PM

    In worksheet on average interest we will solve 10 different types of question. Find the average of first 10 prime numbers. The average height of a family of five is 150 cm. If the heights of 4 family

    Read More

  3. How to Find the Average in Math? | What Does Average Mean? |Definition

    May 17, 25 04:04 PM

    Average 2
    Average means a number which is between the largest and the smallest number. Average can be calculated only for similar quantities and not for dissimilar quantities.

    Read More

  4. Problems Based on Average | Word Problems |Calculating Arithmetic Mean

    May 17, 25 03:47 PM

    Here we will learn to solve the three important types of word problems based on average. The questions are mainly based on average or mean, weighted average and average speed.

    Read More

  5. Rounding Decimals | How to Round a Decimal? | Rounding off Decimal

    May 16, 25 11:13 AM

    Round off to Nearest One
    Rounding decimals are frequently used in our daily life mainly for calculating the cost of the items. In mathematics rounding off decimal is a technique used to estimate or to find the approximate

    Read More