While dining out, Chad spent $25.00. If the bill totaled $21.00 before the tip was added, approximately what percent tip did Chad leave?

Calculate the tip amount: Subtract the bill amount before the tip from the total amount he paid, including the tip.
Tip amount = $25.00 (total paid) - $21.00 (bill before tip) = $4.00
Divide the tip amount by the bill amount before the tip and multiply by 100% to express it as a percentage:
Tip percentage = ($4.00 tip amount) ÷ ($21.00 bill) × 100% ≈ 19%
Therefore, Chad left an approximate tip of 19%.