Problem Solving

If the selling price is doubled,the profit is trippled,what is the percentage of profit??

1) 50%
2) 100%
3) 150%
4) 200%
5) 250%

nahid078 wrote:If the selling price is doubled,the profit is trippled,what is the percentage of profit??

1) 50%
2) 100%
3) 150%
4) 200%
5) 250%

When c is cost price and p is profit, the selling price is c + p and the percentage of profit is (p/c) 100%. But, when the selling price is made 2 (c + p), the profit becomes 3p, proving that

2 (c + p) - p = 3p,

or 2 c = 2 p,

or c = p.

Hence, (p/c) 100% = [spoiler]100%.

Second option. [/spoiler]

nahid078 wrote:If the selling price is doubled, the profit is tripled, what is the percentage of profit?

1) 50%
2) 100%
3) 150%
4) 200%
5) 250%

An alternate approach is to PLUG IN THE ANSWERS, which represent the original mark-up.
Let the cost = 100.

Answer choice D: 200%
Original profit = 200% of 100 = 200.
Original selling price = cost + profit = 100 + 200 = 300.
Doubled selling price = 2*300 = 600.
New profit = (new selling price) - (cost) = 600-100 = 500.
Since the profit increases from 200 to 500, it does NOT quite triple.
Eliminate D.

Answer choice B: 100%
Original profit = 100% of 100 = 100.
Original selling price = cost + profit = 100 + 100 = 200.
Doubled selling price = 2*200 = 400.
New profit = (new selling price) - (cost) = 400-100 = 300.
Since the profit increases from 100 to 300, it TRIPLES.

The correct answer is B.

Suppose I have a $100 watch that I normally sell for $x.

My normal profit = $(x - 100).

But if I sell the watch for $2x, my profit is $(2x - 100).

We're told that this TRIPLES the profit, so

(2x - 100) = 3 * (x - 100)

or

x = 200.

So I normally sell the watch for $200, which represents a 100% profit.