If they give you the total price and the price after the discount you can use this "formula" to solve it p/100=b/a where p is the percentage, a is the total price and b is the price after the discount.
Answer:
Profit = Rs 100
Profit %age = 6.25%
Step-by-step explanation:
Cost Price = Rs 80
Cost Price for 20 kg = Rs 1600
Selling Price = Rs 85
<u><em>Profit for 1 kg</em></u> = Rs 85 - Rs 80
=> Rs 5 (For 1 Kg)
<u><em>Profit for 20 kg:</em></u>
=> Rs 5*20
=> Rs 100
<u><em>Now Profit %age:</em></u>
=> 
=> 0.0625 * 100
=> 6.25%
in order to know the greatest common multiple of 84 you would have to compare it to another number