Bunuel
An article is sold at 20% profit. If its cost price is increased by $50 and at the same time, if its selling price is also increased by $30, the percentage of profit decreases by \(\frac{10}{3}\)%. Find the cost price.
(A) 650
(B) 850
(C) 1000
(D) 3000
(E) 4500
Solution:
Let the original cost of the article be c. Since the article is sold at a 20% profit, the profit is 0.2c, and the sale price is 1.2c.
If the cost is increased by $50 and the selling price is increased by $30, then the new profit is (1.2c + 30) - (c + 50) = 0.2c - 20.
We are also told that the profit decreases by 10/3 %; thus, the new profit is 20 - 10/3 = 50/3 %.
Recall that the new cost is c + 50 and the new profit is 0.2c - 20; thus, in terms of c, the percentage of profit is [(0.2c - 20) / (c + 50)] * 100. Let’s set this expression equal to 50/3:
[(0.2c - 20)/(c + 50)] * 100 = 50/3
(0.2c - 20)/(c + 50) = 50/300 = 1/6
1.2c - 120 = c + 50
0.2c = 170
c = 170/0.2 = $850
Answer: BCan you please explain how to figure % profit decrease by 10/3% as (20-10/3)% and not (20 - (10/3% of 20))?