[kenny1999]

while glass is said to be brittle and it is easy to break as a 3 years old kid knows that throwing a glass bottle on ground will certainly break. But why we need to use the glass, the hardest material on the earth, to cut glass? So should glass be strong or brittle?

[BetaAmyloid]

Glass isn't the hardest material on earth AND it is strong yet brittle - such as diamond is.

Your question is confusing.