Bài 6 : Một khu đất hình chữ nhật có chiều dài 100m, chiều rộng bằng 3/4 chiều dài.Người ta danh ra 25% diên tích đất để đào ao thả cá. Tính diện tích đất đào ao? .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. Bài 7 : 3/4 số gạo của cửa hang là 382,5 tạ.Tìm 40% số gạo của cửa hang đó? .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. Bài 8 Tính bằng cách thuận tiện nhất : a) 36,4x 99 + 36+0,4 b)77,28x 20,2 + 23,72x 20,2-20,2 .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. c)1,25x59,7 x800 d)2,5x 46 + 54 x 2,5 .................................................................................................................................................................................. .................................................................................................................................................................................. ..................................................................................................................................................................................