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Please help me with the following questions: 1) 25% of 90 is what number? 2) 7% of 80...

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maganda123 | (Level 1) Honors

Posted October 22, 2008 at 3:51 PM via web

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Please help me with the following questions:

1) 25% of 90 is what number?

2) 7% of 80 is what number?

3) What percent 38 is 3.8?

4) 70.6 is what percent of 635.4?

Please help me solve these four problems.

8 Answers | Add Yours

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ladyvols1 | High School Teacher | (Level 3) Senior Educator

Posted October 22, 2008 at 11:31 PM (Answer #1)

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25% of 90 is what number?  .25 times 90 equals 22.5

7% of 80 is what number?   .07(80) = 5.6

N% of 3.8 is 38? n%(3.8) = 38; n= 38 divided by 3.8 ; n = 10%

70.6 is what percent of 635.4;  70.6= n%(635.4)

70.6 divided by 635.4 = n%  ;  n = 11.11%  repeating 1

 

Sources:

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mizladyj | High School Teacher | eNotes Newbie

Posted October 23, 2008 at 1:43 PM (Answer #2)

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1) .25*90=x

   the number is 22.50

2) .07*80 =x

the number is 5.60

3)x/100*3.8=38

3.8x=3800

the percent is 1000%

4)70.6*x/100=635.4

70.6x=63540

the percent is 900%

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atwama | eNotes Newbie

Posted March 17, 2009 at 8:07 PM (Answer #3)

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Follow these simple steps for each question.

Q1. 25% of 90 is what number?

i) Express 25% as: % (25/100); fraction (¼, when simplified by dividing through with 25); or decimal (0.25, when you divide 25 by 100 or get the inverse of ¼)

 

ii) Now, you can multiply 90 by any three expressions - 25/100, ¼, 0.25 - to calculate your answer. They should give the same result. Let's check!

 

25/100 x 90 = 25/100 x 90/1

                    = (25 x 90)/(100 x 1)

                    = 2250/100

                    = 22.5

 

¼ x 90 = (1 x 90)/(4 x 1)

            = 90/4

            = 22.5

or,

 

0.4 x 90 = 22.5

Q2. 7% of 80 is what number?

Follow the same steps above and you get: 7/100 or 0.07. Now use (multiply) either 7/100 x 80, or 0.07 x 80 to calculate your answer. Let's calculate then,

7/100 x 80 = 7/100 x 80/1

                  = (7 x 80)/(100 x 1)

                  = 560/100

                  = 5.6

or,

 

0.07 x 80 = 5.6

Q3. What percent of 3.8 is 38?

i) Define your unknown (%), say x, as an equation.

So your equation becomes: 3.8x = 38.

ii) Now solve for x

3.8x = 38

Isolate x, so

(3.8/3.8)x = 38/3.8

              x = 10

Answer: 10%

iii) Check answer: Substitute x = 10 into the equation: 3.8x = 38, so

3.8x = 38, where x = 10

3.8(10) = 38

       38 = 38

    LHS = RHS so answer is correct!

Q4. 70.6 of what % of 635.4?

i) Apply the same rules as in Q3, so your equation becomes: 70.6x = 635.4

ii) Now solve for x

70.6x = 635.4

Isolate x, so

(70.6/70.6)x = 635.4/70.6

              x = 9

Answer: 9%

iii) Check answer: Substitute x = 9 into the equation: 635.4x = 70.6, so

635.4x = 70.6, where x = 9

70.6(9) = 635.4

   635.4 = 635.4

    LHS = RHS so answer is correct!

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revolution | College Teacher | (Level 1) Valedictorian

Posted July 4, 2010 at 5:06 PM (Answer #4)

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1) 25% of 90= 25/100 * 90

= 1/4 *90

= 22.5

2) 7% of 80= 7/100*80= 5.6

3) 38/3.8 = 10%

4) 70.6/635,4 * 100= 11.1% ( to three sig. fig.)

 

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atyourservice | Student, Grade 10 | (Level 3) Valedictorian

Posted May 26, 2014 at 1:37 AM (Answer #5)

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1) 25% of 90 is what number? 90 x .25 = 22.5

2) 7% of 80 is what number? 80 x .07 = 5.6

3) What percent 38 is 3.8? 38 / 3.8 = 10 so 10%

4) 70.6 is what percent of 635.4? ( 70.6 / 635.4 ) x 100 = 11%

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kevin0001 | Student, Grade 9 | (Level 1) Salutatorian

Posted August 14, 2014 at 5:19 AM (Answer #6)

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1. 25% of 90        To solve this, turn 25% into a fraction. After it is a fraction,                                multiply it by 90 to find 25% of 90. 90 x .25 = 22.5

2. 7% of 80          Same as the first question, turn the percent into a fraction and                            multiply them. 80 x .07 = 5.6

3. percent 38 is 3.8     Divide 38 by 3.8 to find out what percent. 38 / 3.8 = 10%

4. 70.6 is what percent of 635.4      First write the equation down as a cross                                                           multiplication problem.  70.6 / 635.4 = ? /                                                          100 . Then multiply 70.6 and 100. After you                                                     have done all that, then divide the product                                                         by 635.4.        7060 / 635.4 = 11.1% 

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givingiswinning | Student, Grade 10 | (Level 1) Valedictorian

Posted August 16, 2014 at 1:13 AM (Answer #7)

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1) 90 x .25 = 22.5

2) 80 x .07 = 5.6

3) 38 / 3.8 = 10 so 10%

4) ( 70.6 / 635.4 ) x 100 = 11%

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malkaam | TA , Undergraduate | (Level 1) Valedictorian

Posted October 14, 2014 at 8:19 PM (Answer #8)

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1) 25% of 90 is what number?

let x b the number,

hence, x=25% of 90

x=25% * 90

x= 25/100 * 90

x= .25*90

x= 22.5

2) 7% of 80 is what number?

let x be the number,

hence, x= 7% of 80

x=7% * 80

x= 7/100 * 80

x= 0.07 * 80

x= 5.6

3) What percent 38 is 3.8?

let x be the percent,

x% of 38 = 3.8

x% * 38 = 3.8

x% = 3.8/38

x% = 0.1

x/100 = 0.1

x= 0.1*100

x= 10%

4) 70.6 is what percent of 635.4?

let x be the percent:

x% of 635.4 = 70.6

x/100 * 635.4 =70.6

x/100 = 70.6/635.4

x/100 = 0.111

x= 100*0.111

x= 11%

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