bn AN cho 2 bn BÌNH và LAN số viên bi là:

80-(10+20)=50( viên bi)

 đáp số:  50 viên bi

tik mk nha Khởi My

60% = 3/5

nưa chu vi là

160 : 2 = 80 (m)

chiều dài là

80 : (3+5) x 5 = 50 (m)

chiều rộng là

80 - 50 = 30 (m)

diện tich hình chữ nhật là

50 x 30 = 1500 (m2)

2125cm2 nhé

Ủng hộ tớ đi

In 1783, two French brothers built the first balloon to take people into the air. One hundred and twenty years .later.., in 1903, the Wright brothers built the first plane with an engine and flew in it. This was .in.. the United States. Then, in 1918, the US Post Office began the first airmail service.

Aeroplanes changed a lot in the next thirty years. Then, in the 1950s, aeroplanes became much .faster.. because they had jet engines.

In 1976, Concorde was built in the UK and France. It was the fastest passenger plane in the world at that time and it .can.. fly at 2300 kilometres an hour, so the journey from London to Newyork was only four hours.

Today, millions of people travel .by.. aeroplane, and it is difficult to think of a world without them.