Solution -
Let,
The CP of 1 cm = 1
CP of 100 cm = 100
He marks-up goods by 20%.
MP = 100 (120/100)
MP = 120
Here,
SP = MP
SP = 120
But,
The shopkeeper measures 20% less for every metre of the cloth.
So,
CP of 80 cm = 80
Profit % = [(SP - CP) / CP] × 100
= [(120 - 80) / 80] × 100
= (40 / 80) × 100
= 100/2
= 50
Thus,
The profit percentage is 50%.
Hence,
The correct anwer is option (a) 50%.
Thank you