To find the percentage change from 30 to 40, we need to first calculate the difference between the two numbers.

Step 1: Difference = Final Value - Initial Value

Difference = 40 - 30

Difference = 10

Step 2: Next, we need to find the absolute value of the difference. This is because percentage change is always calculated as a positive value.

Absolute Difference = |Difference|

Absolute Difference = |10|

Absolute Difference = 10

Step 3: Now, we can calculate the percentage change using the formula:

Percentage Change = (Absolute Difference / Initial Value) x 100

Percentage Change = (10 / 30) x 100

Percentage Change = 33.33%

Therefore, the percentage change from 30 to 40 is 33.33%. This means that there was an increase of 33.33% from 30 to 40.