sanju09 wrote:A dealer decides to sell his goods at cost price but still gains 25 percent. How many grams does he give instead of a kg, if a kg equals to 1000 grams?
(A) 720
(B) 750
(C) 800
(D) 850
(E) 900

Let the CP be Rs.X for 1000 g
let he sells only Yg for Rs. X
so SP for Y gm = X
CP for Y gm = YX/1000
profit (SP-CP)/CP x100 =25
--> (X- (XY/1000))/(XY/1000) x 100 = 25 --> (1000-Y)/Y = 0.25 --> 1000-Y = 0.25 Y -->Y = [spoiler]1000/1.25= 800 g Ans C[/spoiler]

sanju09 wrote:A dealer decides to sell his goods at cost price but still gains 25 percent. How many grams does he give instead of a kg, if a kg equals to 1000 grams?
(A) 720
(B) 750
(C) 800
(D) 850
(E) 900

if the dealer sells at the cost price while making profit, he would have increased price/kg and would have sold less quantity.

i.e

(price/kg) * (quantity) = selling price.

we're given that increase in price/kg is 25% i.e 1/4, therefore as the quantity sold is inversely proportional to it, actual quantity would have been 1/5th less or 20%less.
[spoiler]
i.e he would have sold 1000 - 1/5 * 1000 = 800 gms. [/spoiler]

For the dealer to earn 25% he has to reduce the quantity by 20%.
answer C

It's like he has to sell 4 parts as 5 parts to make a profit of 25% keeping the C.P. same. And that is possible if he takes 0.2 parts from each of 4 original parts.

HTH!!

An honest dealer to make 25% profit will sell at Cost Price (CP) + 0.25 CP = 5/4 CP

so
If Selling Price is 5/4 CP quantity sold = 1 kg
If SP is 1 CP quantity sold = 1/ (5/4) = 4/5 kg = 800 gms
solving by Unitary method.
The dishonest trader keeps his SP = CP
but reduces the quantity.