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Question:


maganda123

1)25% of 90 is what number?

2)7% of 80 is what number?

3)what percent of 3.8 is 38?

4)70.6 is what percent of 635.4?

there are 4 questions.

please help me solve these problems.

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Posted by maganda123 on Wednesday October 22, 2008 at 11:51 PM and tagged with division, math, percents.

Answers:


  1. ladyvols1 Teacher
    High School - 9th Grade

    eNotes Editor

    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:
    http://www.enotes.com/sat-prep/introduction
    http://www.purplemath.com/modules/percntof.htm

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    Posted by ladyvols1 on Thursday October 23, 2008 at 7:31 AM

  2. mizladyj
    mizladyj Teacher
    High School - 10th Grade

    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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    Posted by mizladyj on Thursday October 23, 2008 at 9:43 PM

  3. atwama
    atwama

    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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    Posted by atwama on Wednesday March 18, 2009 at 4:07 AM