A shopkeeper advertises for selling cloth at 4% loss. However, by using a false meter scale he actually gains 20% . What is the actual length of the scale___________?

65 cm

55 cm

40 cm

90 cm

80 cm

Let the percentage deduction in weight be y%

y−4100−y×100=20⇒y−4100−y=15⇒5y−20=100−y⇒6y=120⇒y=20

Hence, for a meter, length used = (100 - 20)% of 1 m

= 80% of 100 cm = 80 cm