Homework Help

1)tickets decreased from $90.00 to $85.002)a $170.00 bicycle decreased to $155.00there...

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maganda12 | eNoter

Posted October 22, 2008 at 3:55 PM via web

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1)tickets decreased from $90.00 to $85.00

2)a $170.00 bicycle decreased to $155.00

there are 2 questions.

please help me find the percent of decrease for each of the following items.

4 Answers | Add Yours

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adrigon | High School Teacher | (Level 2) Adjunct Educator

Posted October 22, 2008 at 6:27 PM (Answer #1)

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Both of these are simple percentage problems. Your percentage formula is, as always:

p/w=%/100

where the part of the whole is equal to the percentage over 100.

So in this case, your part for number 1 is $5 (the amount decreased) and your whole is $90. Your percentage is unknown, so let's call that X. So your re-written formula should be:

$5/$90 = X/100

This is a proportion, so we can cross-multiply, so:

$5 x 100 = 500

$90 x X = 90X

So now we have 90X = 500.

In order to isolate X, we need to divide 90 from both sides.

90X / 90 = X

500 / 90 =  5.56

So, X = 5.56, and therefore the price decreased by 5.56%.

For number 2, your part is $15, your whole is $170, and again your percentage is unknown, X.

$15/$170 = X/100

So again, we cross-multiply, and get:

$15 x 100 = 1500

$170 x X = 170X

And therefore,

1500 = 170X

 Now we isolate X by dividing out the coefficient from both sides.

170X / 170 = X

1500 / 170 = 8.82

Therefore, X = 8.82%, your percentage of decrease.

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cburr | Middle School Teacher | (Level 2) Associate Educator

Posted October 26, 2008 at 11:00 AM (Answer #2)

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This might be an easier way to think about it.

In the first problem, the amount of decrease is $5.  What you need to find is what percent $5 is of $90 (since $90 is the number you started with).

Percent problems can always be solved using: 

Part / Whole = %  

Just plug in what you know and solve it to find the missing piece.  Here, you know the part ($5) and the whole ($90). 

So, the % = $5 / $90 = .0555555 etc

Remember that .05 is the same as 5%.  So, just round the answer to however many places your teacher wants. 

.0555555 etc = .0556 (5.56%) or .056 (5.6%) or .06 (6%) depending on how exact you need to be.

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revolution | College Teacher | Valedictorian

Posted July 4, 2010 at 5:47 PM (Answer #3)

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1) The tickets decreashed from 90 dollars to 85 dollars, so the price change is 5 dollars.

Percentage decrease= decrease/ original amount * 100% so:

% decrease= 5/90 * 100%= 5.55%

2) The price change is 170-155= 15 dollars

% decrease= 15/170*100%= 8.82%

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atyourservice | TA , Grade 10 | Valedictorian

Posted May 26, 2014 at 1:44 AM (Answer #4)

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1)tickets decreased from $90.00 to $85.00

90-85=5

5/90 x 100 = 5.55%

2)a $170.00 bicycle decreased to $155.00

170 - 155 = 15

15/170 x 100= 8.82%

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