A glass when full of milk weighs one kg. When half full, it weighs 3/4 kg. What is the weight (in kg) of the empty glass?

Question: A glass when full of milk weighs one kg. When half full, it weighs 3/4 kg. What is the weight (in kg) of the empty glass?

Solution:
Let,
Weight of the empty glass = g kg
Weight of milk when the glass is full = m kg

Given,
g + m = 1 ........(1)
and when the glass is half full = g + (m/2) = 3/4 ..........(2)

Subtracting the second equation from the first.
⇒ m - (m/2) = 1 - (3/4)
⇒ m/2 = 1/4
⇒ m = 2/4
∴ m = 1/2

Therefore, g = 1 - (1/2) = 1/2 = 0.5 kg