A wholesaler sells a watch to a retailer at a gain of 36% and the retailer sells it to a customer at a loss of 25%. If the customer pays Rs 2499, what had it cost the wholesaler?

For the wholesaler,

Let the cost price = Rs. $$100x$$

With profit of 36%, Selling price = $$\frac{136}{100} \times 100x = Rs. 136x$$

For the retailer,

Cost price = Rs. $$136x$$

With a loss of 25%, Selling price = $$\frac{75}{100} \times 136x = Rs. 102x$$

For the customer,

Cost price = $$102x = 2499$$

=> $$x = \frac{2499}{102} = \frac{49}{2} = 24.5$$

$$\therefore$$ Cost price for retailer = $$100 \times 24.5 = Rs. 2450$$