COIN CONCEPT

When 2 quantities are sold as a group together .
Example- A horse and a carriage were bought for Rs. 12000. the carriage was sold at a loss of 10% , horse was sold at a profit of 20%. Together I received Rs.13500. what is the C.P. and S.P. of each.

Method-Assume everything to be a horse, so I shud have sold everything at 20% profit.20% of 12000+12000= 14400.But I received Rs. 13500 only that makes a difference of 900 or Rs. 900 are less. This also makes a difference of 30% coz we calculated 40% profit (20+20%), but we had [+20%+(-10%)]=10%
I calculated 30% more on carriage.
30% or carriage=900
therefore 100%=3000
so now we have the individual cost of the horse, the carriage is for 9000/-and the S.P. can b calculated now.