Mot mieng ton hinh chu nhat co chieu dai 60cm chieu rong bang 2/3 chieu dai nguoi tho cat bo 4 hinh vuong bang nhau o 4 goc moi hinh vuong co canh 5cm Sau do nguoi tho gap Phan con lai thang 1 cai hop ko co nap Tinh kich thuoc cua cai hop
dien tich cua tung mat cua hop do