A shopkeeper sold 24 shirts, each at a profit of 20%, and 16 shirts, each at a profit of 10%. If he had sold all 40 shirts, each at a profit of 15%, then his overall profit would have been reduced by ₹36. What is the cost price of each shirt?

Let's assume the cost price of each shirt is Rs. 100y.

A shopkeeper sold 24 shirts, each at a profit of 20%.

Selling price of 24 shirts = $$24 \times\ 100y$$ of (100+20)%

= 2400y of 120%

= 2880y    Eq.(i)

16 shirts sold, each at a profit of 10%.

Selling price of 16 shirts = $$16 \times\ 100y$$ of (100+10)%

= 1600y of 110%

= 1760y    Eq.(ii)

If he had sold all 40 shirts, each at a profit of 15%, then his overall profit would have been reduced by ₹36.

Selling price of 40 shirts = $$40 \times\ 100y$$ of (100+15)%

= 4000y of 115%

= 4600y    Eq.(iii)

Eq.(i)+Eq.(ii) = Eq.(iii)+36

2880y+1760y = 4600y+36

4640y = 4600y+36

4640y-4600y = 36

40y = 36

y = 0.9

Cost price of each shirt = 100y

= $$100\times0.9$$

= ₹90