Joint Variation: Group 3
Joint Variation: Group 3
Joint Variation: Group 3
Group 3
What is Joint Variation?
• Joint Variation refers to a scenario in which the
value of one variable depends on two, or more,
other variables when the other variables are held
constant.
y = kx
'' y varies jointly as x and z ''
''y is proportional to x and z''
2
a = kbc a = 36 b = 3 c = 4
z = kxy z = 60 y = 6 x = 5 z = 2xy x = 7 y = 6
60 = k(5)(6) z = 2(7)(6)
60 = 30k z = 84
60/30 = 30k/30
2=k
1. The variable x is in joint variation with y and z. When the values of y and z are
4 and 6, x is 16. What is the value of x when y = 8 and z =12?
Solution:
The equation for the given problem of joint variation is x = Kyz where K is
the constant.
Solution:
From the given problem equation for the joint variation is A = KBC2
From the given data value of the constant K is K = BC2A K = 4×3^21/44 = 36/144 =
¼.
Substituting the value of K in the equation A = BC24 A = 6×424 = 24
3. The area of a triangle is jointly related to the height and the base of the
triangle. If the base is increased 10% and the height is decreased by 10%, what
will be the percentage change of the area?
Solution:
We know the area of triangle is half the product of base and height. So the joint
variation equation for area of triangle is A = bh2bh2 where A is the area, b is
the base and h is the height. Here 1212 is the constant for the equation.
Base is increased by 10%, so it will be b x 110100110100 = 11b1011b10.
Heightis decreased by 10%, so it will be h x 9010090100 = 9h109h10. So
the new area after the changes of base and height is 11b10×9h10211b10×9h102
= (9910099100)bh2bh2 = 9910099100A. So the area of the triangle is decreased
by 1%.
4. A rectangle’s length is 6 m and width is 4 m. If length is doubled and width is halved, how much the
perimeter will increase or decrease?
Solution:
Formula for the perimeter of rectangle is P = 2(l + w) where P is perimeter, l is length and w is width.
So P = 2(6 + 4) = 20 m