According to the question the metre scale having a weight of 50‌gf is balanced at 40 cm mark without any weight suspended on it. So, its weight acts at 40‌cm mark which is also the centre of gravity of this non-uniform metre scale.
Thus, 0‌cm to 40‌cm length will have a weight of 25‌gf
And, 40‌cm to 100‌cm length will have a weight of 25‌gf.
Thus, if we cut this ruler from 50‌cm mark (i.e. centre), the part 0 to 50‌cm part of the ruler will weigh more than 25‌gf.