# Proportion

See how to solve a proportion

(colon form, fraction form).

2 examples and their solutions.

## Colon Form

### Formula

a : b = c : d

→ a⋅d = b⋅c

→ a⋅d = b⋅c

### Example

(2x + 1) : 3 = x : 2

Solution (2x + 1) : 3 = x : 2

(2x + 1)⋅2 = 3⋅x - [1]

4x + 2 = 3x

4x - 3x = -2

x = -2

(2x + 1)⋅2 = 3⋅x - [1]

4x + 2 = 3x

4x - 3x = -2

x = -2

Close

## Fraction Form

### Formula

ab = cd

→ a⋅d = b⋅c

→ a⋅d = b⋅c

### Example

x2 = 4x - 15

Solution x2 = 4x - 15

x⋅5 = 2⋅(4x - 1) - [1]

5x = 8x - 2

5x - 8x = -2

-3x = -2

x = 23

x⋅5 = 2⋅(4x - 1) - [1]

5x = 8x - 2

5x - 8x = -2

-3x = -2

x = 23

Close