user-avatar
truongkim754
2 năm trước
a) 5km2 = ......m2 b) 23m2 73dm2 = ......dm2.
Thích Trả lời Chia sẻ

Các câu hỏi liên quan

Ballpoint pen is a pen that has, as its name says, ball at its point which rotates when dragged across the writing surface and leaves behind ink that comes from the reservoir of the pen. Ball at the point can be of different diameter and can be made of brass, steel, or tungsten carbide. It is today the most widespread writing instrument and has literally changed the way we write. Trying to invent a pen which can write on leather, a tanner John J. Loud invented the first ballpoint pen and patented it in 1888 in America. This pen had a small steel ball which was placed so it could not fall out nor fall in but it still could rotate freely. This invention was not commercially viable and could not be used for writing. Because of that patent lapsed in time. 1. Where does the ink come from? ________________________________________________ 2. What can ball at the point be made of? ________________________________________________ 3. Who invented the first ballpoint pen? ________________________________________________ 4. Was this invention commercially viable? ________________________________________________

2018 © Loga - Không Ngừng Sáng Tạo - Bùng Cháy Đam Mê
Loga Team