If
a
b
=

c
d
then, a × d = b × c

If
a
b
=

c
d
then, a × d = b × c

Solve for x if
5
x

=
10
16

The proportion becomes
5
8

=
10
16

5
x

=
10
16

Solve for n if
8
10

=
n
25

200
10

=
10n
10

If
a
b

=
c
d
then,

a + b
b

=
c + d
d

x  8
8

=
6
4

x  8 + 8
8

=
6 + 4
4

x
8

=
10
4

If
x
y

=
x
4
then, y = 4

For instance If
50
y

=
50
100
then, y = 100

If
18
y

=
x
y
then, x = 18

If
a
b

=
c
d
then,

a + c
b + d

=
a
b

a + c
b + d

=
a
b

Say you have
x + 2
8 + 4

=
x
8

It is equivalent to
x
8

=
2
4

Solve for x if
5
x

=
10
16

The proportion becomes
5
8

=
10
16

5
x

=
10
16

Solve for n if
8
10

=
n
25

200
10

=
10n
10

If
a
b

=
c
d
then,

a + b
b

=
c + d
d

x  8
8

=
6
4

x  8 + 8
8

=
6 + 4
4

x
8

=
10
4

If
x
y

=
x
4
then, y = 4

For instance If
50
y

=
50
100
then, y = 100

If
18
y

=
x
y
then, x = 18

If
a
b

=
c
d
then,

a + c
b + d

=
a
b

a + c
b + d

=
a
b

Say you have
x + 2
8 + 4

=
x
8

It is equivalent to
x
8

=
2
4

Sep 25, 15 11:35 AM
Learn what compensation is in math. See how to use compensation to do mental math
Sep 24, 15 06:19 PM
Learn what cryptarithms are and how to solve them