Changing the Subject in an Equation or Formula
In algebra we will learn how to find the value of the variables by changing the subject in an equation or formula using the balance method.
To find the value of the variable using change of subject of formula and method of substitution:
The process of finding the value of algebraic expression by replacing the variables by the given value is called the method of substitution.
In this,
• Make the required variable as the subject.
• Substitute the values of all the variables except the subject.
• Now simplify and find the value of the subject.
Worked-Out Examples on Changing the Subject in an Equation or Formula
1. In the formula P = 2(l + b), find b when P = 36 cm and l = 10 m
Solution:
P = 2 (l + b)
P = 2l + 2b
P - 2l = 2b
(P - 2l)/2 = 2̶b/2̶
i.e., b = (P - 2l)/2
b = (36 - 2 × 10)/2
b = (36 - 20)/2
b = 1̶6̶/2̶
b = 8
2. Given A = P {1 + (r/100)}ⁿ make r as the subject.
Given A = 1102.50 P = 1000 n = 2, find r.
Solution:
A = P {1 + (r/100)}ⁿ
A/P = {1 + (r/100)}ⁿ
(A/P)1/n - 1 = r/100
100 {(A/P)1/n - 1} = r
Therefore, 100 {(A/P)1/n - 1}
Substituting the values of A, P and n we get;
r = 100 {(1102.50/1000)1/2 - 1}
= 100 {(110250/1000)1/2 - 1}
= 100 {(441/400)1/2 - 1}
= 100 [{(21/20)2}1/2 - 1]
= 100 {(21/20)
= 100 {21/20 - 1}
= 100 {(21 – 20)/20}
= 1̶0̶0̶ × 1/2̶0̶
= 5
● Formula
Formula and Framing the Formula
Change the Subject of a Formula
Changing the Subject in an Equation or Formula
Practice Test on Framing the Formula
● Formula - Worksheets
Worksheet on Framing the Formula
Worksheet on Changing the Subject of a Formula
Worksheet on Changing the Subject in an Equation or Formula
7th Grade Math Problems
8th Grade Math Practice
From Changing the Subject in an Equation or 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.