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In today’s Mathematics class, We will be discussing Change of Subject of Formula. We hope you enjoy the class!
CHANGE OF SUBJECT OF FORMULA
A formula is a general equation involving two or more unknowns. An example is the formula a = ¶r^{2 } which gives the area of the circle in terms of its radius r. In this formula, a is called the subject of the formula.
Simplifying a formula by substitution
Example:
 Given mx+c=y, express x in terms of m, c, and y. Find the value of x if y=10, c=2 and m is 4
Solution:
1) mx+c= y, mx=yc
$x=\frac{y\u2013c}{m}$
To find the value of X, when y= 10 , m=4and c=2
X=$\frac{10\u20132}{4}=\frac{8}{4}=2$
Evaluation: If I= PRT
 Make p the subject and find the value of p if I = 10, R= 4, and T= 5.
CHANGING THE SUBJECT OF A FORMULA
When a variable which forms a part of the formula is made subject, we say we have changed the subject of the formula.
Examples:
 In the formula S=2¶r(r+h), make h the subject.
 Make m the subject if $F=\frac{mv\u2013mu}{T}$
Solution:
1) S=2¶r(r+h)
S=2¶r^{ 2 }+2¶rh
S 2¶r^{ 2 }=2¶rh
S2¶r^{2} =h
2¶r
2) $F=\frac{mv\u2013mu}{T}$
Cross multiply: FT =mvmu
FT =m(vu)
$\frac{FT}{v\u2013u}=m\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}m=\frac{FT}{v\u2013u}$
EVALUATION
 Make r the subject if V =¶r^{ 2}h
 Make u the subject if 1/f =1/v + 1/u
READING ASSIGNMENT
 Exam focus for J.S.C.E Pg. 212 216
 Essential Maths for J.S.S.3 Pg. 4754
WEEKEND ASSIGNMENT
 Express a in terms of u, v, and t in v= u+at

 (a) a = vut
 (b) a= vu
 (c) a = $\frac{v+u}{t}$

 If Z=2p +3, find the value of Z when p=1. (a) Z=2, (b) Z= 5, (c) Z =7
 In the relation X = $\frac{m\u20136y}{6}$ , how would you write m in terms of x and y?
(a) m=x6 (b) m = 6x 6y (c) m =6x +6y
 Express n in terms of s, a, and L if $S=\frac{n}{2(a+L)}$
$\left(a\right)n=\frac{2(a+L)}{Sa+L}\left(b\right)n=\frac{2S}{a+L}\left(c\right)n=2S\u2013(a\u2013L)$
 Make U the subject if V^{2 }= U^{2 } +2as.
(a) U= V^{ 2} 2as (b) U = (V^{ 2 }2as)^{ 2 } (c) V^{2 } – 2a
THEORY
 Given L = ar^{n1}, make a the subject of the formula.
 If S + $\frac{2t}{d}$, make t the subject of the formula. Find the value of t if S=1, d= 2.
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In our next class, we will be talking about Measure of Central Tendency. We are very much eager to meet you there.
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V=u+2as
Please i am a student, and i don’t understand the 2 last examples in changing the subject of a formula. Please can you deeply explain for us.