A buys water cooler at some price and sells it to B at 20% profit. B sells it to C at 10% profit. If C bought it for ₹6666, then the cost price for B is:

A buys water cooler at some price and sells it to B at 20% profit.

Let's assume the cost price of water cooler for A is ₹100y.

Selling price for A = Cost price for B = 100y of (100+20)%

= 100y of 120%

= 120y

B sells it to C at 10% profit.

Selling price for B = Cost price for C = 120y of (100+10)%

= 120y of 110%

= 132y

If C bought it for ₹6666.

132y = 6666

y = 50.5

Cost price for B = 120y = $$120\times50.5$$

= ₹6060