Cross Multiplication.

1
Cross Multiplication.
4x 16 ..
2
Cross Multiplying Fractions.
Consider the fractions below
To cross multiply we multiply across the equal
sign as shown by the arrows
3 x 8

4 x 6
24

24
Now try these ones yourself.
(1)
(3)
(2)
18 18
70 70
48 48
3
Equation Solving
We can now use the cross multiplication technique
to solve equations.
Solve
(1) Cross multiply the equation.
(2) Solve as normal.
8x

4 x 6
24
x

8
The answer is telling you that three quarters is
the same as six eighths.
x 3
4
Further Example.
Solve
(1) Cross multiply the y term first.
(2) Solve as normal.
6y
7 x 8

y

56
6
y

y

5
What Goes in The Box ?
Solve the following equations using cross
multiplication.
(1)
(4)
x 2
(2)
(5)
w 12
(3)
(6)
f 14