HKIMO 2018 Grade 6 National Final (Heat) Set 03 Question 19

A square is formed from 150 rectangles measuring 2 cm by 3 cm. Find the decrease in total perimeter, in cm.

Source glossary (English–Vietnamese): Square: hình vuông; Rectangle: hình chữ nhật; Decrease: giảm đi; Perimeter: chu vi.