Dishonest Shopkeeper#!#equal selling price

A dishonest shopkeeper sells goods at his cost price but uses a weight of 900 gm for a kg. weight. Find his gain percent.

By selling 100 pens, a shopkeeper gains the selling price of 40 pens. Find his gain per cent.

By selling 8 dozen pencils, a shopkeeper gains the selling price of one dozen pencils. Find his gain per cent.

By selling 8 dozen pencils, a shopkeeper gains the selling price of 1 dozen pencils. What is the gain?

By selling 100 pencils,a shopkeeper gains the selling price of 20 pencils.Find his gain percent

A dishonest shopkeeper sells the items at cost price.But,for every kg he gives 200gm less.His profit percentage is

A dishonest shopkeeper professes to sell pulses at his cost price but uses a false weight of 950 gm for each kilogram. Find his gain percent.