27/10/2020
Date: 22/10/2020
Class: Jss 3
Subject: Maths
Topic:Joint variation
Objective:The student should be able to understand the meaning of joint variation and the calculations that involve in joint variation.
Content: meaning of joint variation. The mass of a sheet of metal is proportional to both the area and the thickness of the metal. Therefore M~AT( my student please use the sign (varies )i gave you in my last class.l don't have the varies signs on my phone kindly bear with me)
For example the T°C inside a house is proportional to the outside temperature, S°C is inversely proportional to the thickness of the house walls, tcm.in this case T~S/t. This is another example of joint variation.
Example 1: x~y/z when y=7, z=3, x= 42.
a. Find the relationship between x, y and z
b. Find x when y= 5 and z= 9
Solution:
X~y/z
Thus x= ky/z where k is constant
When y= 7 and z= 3, x= 42 :.
X= ky/z
42/1= k× 7/3
Cross multiply
K×7= 42×3
7k=42×3
Divide both side by 7
7k/7= 42×3/7
7 cancelled itself now remain k.
K= 42×3/7
K= 126/7
K=18
a. The relationship between x, y and z is x= ky/z
x= 18y/z
b. Find x when y=5 and z= 9
x= ky/z.
x= 18×5/9 = 90/9 x=10.
Assignment: x~y/z, 27 when y= 9 and z= 2
a. Find the relationship between x, y, and z
b. Find x when y= 14 and z= 12.
