IKMC 2027 - Grades 9-10 - Self-study SET 8 - Thematic Batch 3 Question 20

Tom uses 1×3 and 1×5 rectangular tiles to make five strips, each one square high, of lengths 10,12,16,18,20 squares. He may leave no excess pieces and may not overlap tiles. What is the minimum total number of 1×3 tiles needed?