HKIMO 2019 Grade 6 National Final (Heat) Set 02 Question 19

A square is formed by 324 rectangles measuring 1 cm by 4 cm. Find the decrease in the total perimeter, in cm.

Source glossary (English–Vietnamese): Square: hình vuông; Formed: tạo bởi; Rectangle: hình chữ nhật; Difference: hiệu; Total: tổng cộng; Perimeter: chu vi.