Final answer:
Ali gives Hassan 24 pencils after calculating 20% of his total 120 pencils.
Step-by-step explanation:
When Ali gives 20% of his 120 pencils to Hassan, we need to calculate what 20% of 120 is. To do this, we can convert the percentage into a decimal (by dividing by 100) and then multiply it by the total amount of pencils. So, 20% becomes 0.20 when converted into a decimal. Now, we multiply 0.20 by 120 pencils to find out how many pencils Ali gives to Hassan:
0.20 × 120 pencils = 24 pencils
Therefore, Ali gives Hassan 24 pencils.