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?

Let the cost price for the wholesaler be Rs X.
The wholesaler sells it to the retailer at a profit of 36%, so the cost price for the retailer is:

CP
retailer
​
=X×(1+
100
36
​
)=X×
100
136
​

The retailer sells it to the customer at a loss of 25%, so the selling price for the retailer (which is the price paid by the customer) is:

SP
retailer
​
=X×
100
136
​
×(1−
100
25
​
)=X×
100
136
​
×
100
75
​

Given that the customer pays Rs 2499:

X×
100
136
​
×
4
3
​
=2499
X×
100
34
​
×3=2499
X×
100
102
​
=2499
X=
102
2499×100
​

X=24.5×100=2450
Thus, the cost price for the wholesaler was Rs 2450.