Let total mass of the metre stick be M kg.
Distance between mid-point E and new centre of gravity (DA),
= 50 — 45 = 5 cm
Distance between 12 cm mark and new centre of gravity (CD),
= 45-12 = 33 cm
From principle of moments in equilibrium,
M x DE = (2 x 5) x CD Mx 5 = 10x33 or M =66 g
.’… Mass of the metre stick is 66 g