**SUBJECT: MATHEMATICS**

**CLASS: JSS 3**

**DATE:**

**TERM: 1st TERM**

**REFERENCE BOOKS**

- New General Mathematics by M. F Macrae et al bk 3
- Essential Maths by AJS OluwasanmiBk 3

WEEK EIGHT

**TOPIC: CHANGE OF SUBJECT OF FORMULA**

A formula is a general equation involving two or more unknowns. An example is the formula a = ¶r2 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: mx+c= y, mx=y-c

X= y-c

M

To find the value of X, X= 10-2

4

X= 8/4 =2

Evaluation: If I= PRT

- makep 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= mv-mu

T

Solution: S=2¶r(r+h)

S=2¶r 2 +2¶rh

S- 2¶r 2 =2¶rh

S-2¶r2 =h

2¶r

- F =mv-mu

T

Cross multiply: FT =mv-mu

FT =m(v-u)

FT

v-u = m

**EVALUATION**

- Make r the subject if V =¶r 2h
- 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 47-54

**WEEKEND ASSIGNMENT**

- Express a in terms of u, v, and t in v= u+at
- a = vu-t (b) a= v-u (c) a = v+u

tt

- 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 = m – 6y , how would you write m in terms of x and y?

6

(a) m=x-6 (b) m = 6x -6y (c) m =6x +6y

- Express n in terms of s, a, and L if S=n/2(a+L)

(a) n=2(a+L) (b) n= 2S (c) 2S-(a-L)

Sa+L

- Make U the subject if V2 = U2 +2as.

(a) U= V 2 -2as (b) U = (V 2 -2as) 2 (c) V2 - 2a

**THEORY**

- Given L = arn-1, make a the subject of the formula.
- If S + 2t , make t the subject of the formula. Find the value of t if S=1, d= 2.

d

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