Help for a question on Financial Applications of Percentages

[Tiger17]

Hi I got these questions wrong in a test:

1) Nikita's Designer Dresses has a policy of marking up the cost of all its dresses by 91%. If the selling price of the dress is $300, calculate the cost price.

2) calculate the original marked price of a soccer ball discounted by 20% and on sale for $55.

My workings for the test are as follows as I did not know how to work it out.

1) 300 X 0.91 = 273
300 - 273 = $27
and I did a similar sum for Q 2. I knew it wasn't right but just wanted to put an answer in as best I could. I know there must be a formula and I hope you can help me because we have a common test coming up and these were the only questions I have got wrong on this test.

Thank you.

 

[mmm4444bot]

In the first problem, we're adding 91% of some cost to the cost itself, and the result is 300.

They want this unknown cost, so we could assign a symbol to represent it.

c = cost before markup

Marking c up by 91% would then be

c + 0.91c

and this result is to be 300.

c + 0.91c = 300

Factor out the c, from the lefthand side.

c(1 + 0.91) = 300

Simplifies to

1.91c = 300

Solve for c, by dividing both sides of the equation by 1.91

c=300/1.91

In the second problem, we are subtracting a percentage, instead of adding.

Let c = cost before markdown

c - 0.20c = 55

Can you finish? :cool:

 

[mmm4444bot]

300 X 0.91 = 273

300 - 273 = $27

$27 would be correct, if the question were asking, "$300 less 91% is what?" or "What is 9% of $300?"