A shopkeeper sells wheat at a 20% markup and uses a false weight that is 10% lighter than its labelled weight for weighing. What is his total profit percentage?

It is given in question that the shopkeeper uses a weight $$10\%$$ less than the actual weight for weighing.

Suppose he is selling $$100$$ gm wheat.

But in reality he sells $$100\left(1-\dfrac{10}{100}\right)$$ gm = $$90$$ gm wheat

So on every 90 gm wheat sold, he is making a profit of $$(100-90)=10$$ gm of wheat.

So profit percentage will be = $$\dfrac{10}{90}\cdot100$$ = $$\dfrac{100}{9}\%$$

Also, he is initially making a profit of $$20\%$$

So, overall profit percentage = $$\left(20+\dfrac{100}{9}+20\cdot\dfrac{100}{9}\cdot\dfrac{1}{100}\right)\%$$   (Using successive profit percentage formula)

So, overall profit percentage = $$33.33\%$$