A merchant professes to lose 4% on tea but uses a weight equal to 840 gm instead of 1 kg. Find his real loss% or profit%. Book solution: If cp(cost price) of 1 kg is x , then sp(selling price) of 1 kg = 96/100 x i.e .96x (4% loss). Which is actually sp of 840 gm. cp of 840 gm= x/1000*840=.84x So, when cp =.84x, sp is .96x when cp=100 , sp = .96x/.84x*100=114.28 i.e 14.28% profit My workout: I want to solve it without using the price, like in the above. I know the merchant professes a loss of 4%. i.e instead of giving 100gm tea, he is giving the customer 104 gm tea, i.e a loss of 4 gm tea. Since he uses 840 gm in place of 1 kg. So when he will sell 1 kg tea, he professes a loss of 4% i.e he will give customer 1040 gm tea, which actally will be 840/1000*1040 = 873.6 gm. So he is making a profit of 1000 - 873.6 = 126.4 gm on 1000gm. So on 100 gm, his profit = 12.64%. Whats wrong on my workout. is it that the loss/profit % is always on price? Thank you.