A dishonest dealer professes to sell his goods at Cost Price but still gets 20% profit by using a false weight. What weight does he substitute for a kilogram?

A. 855 1/2 grams
B. 833 1/3 grams
C. 833 1/2 grams
D. 875 2/7 grams
Explanation:
If the cost price is Rs.100, then to get a profit of 20%, the selling price should be Rs.120.
If 120kg are to be sold, and the dealer gives only 100kg, to get a profit of 20%.
How many grams he has to give instead of one kilogram(1000 gm).
120 gm —— 100 gm
1000 gm —— ?
(1000 * 100)/120 = 2500/3 = 833 1/3 grams.