Math Question !

Discussion in 'Math' started by RRITESH KAKKAR, Dec 31, 2015.

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  1. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    Hello
    What percentage should be added to 40 to make it 50?
    Ans 25
    How?
    let
    40+x=50
    x=10?????
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    How many percent is 10 from 40?

    Bertus
     
  3. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    4% i think
     
  4. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    Now my calculator is being used since i buyyed Scientific Fx 82MS
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    4% is not correct.
    If 40 is 100 %, how many percent is 10.

    Bertus
     
  6. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    10/40=0.25
     
  7. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    To calculate percentage decrease: First: work out the difference (decrease) between the two numbers you are comparing. Then: divide the decrease by the original number and multiply the answer by 100. If your answer is a negative number then this is a percentage increase.
     
  8. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    If 40 is 100 %
    100% of 10 is 10/100=0.1
     
  9. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    125 gallons of a mixture contains 20% water. What amount of additional water should be added such that water content be raised to 25%?
     
  10. tjohnson

    Active Member

    Dec 23, 2014
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    This is basic math. Out of the 125 gallons of the mixture, 20% is water, so there are 125 * 0.2 = 25 gallons of water.

    If we want to raise the water content to 25%, we would need 25% of 125 gallons, which is 125 * .25 = 31.25 gallons of water.

    Finding the difference between 25 and 31.25 gallons shows that the amount of water that must be added is 31.25 - 25 = 6.25 gallons.
     
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  11. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    ok, it was so simple.
    I was messing with meaning.
     
  12. tjohnson

    Active Member

    Dec 23, 2014
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    Oops, I was forgetting something important. When water is added, the total amount of mixture changes, so the problem is more complicated than I was thinking:
    0.2(125) + W_added = 0.25(125 + W_added)
    25 + W_added = 31.25 + 0.25W_added
    0.75W_added = 6.25​

    So the correct answer is actually 6.25 / 0.75 = 8.33 gallons of water. Now if you calculate 25% of the total mixture, it equals (125 + 8.33) * .25 = 33.33 gallons, which is 25 + 8.33, proving that this answer is correct.
     
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  13. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    125 gallons of a mixture contains 20% water. What amount of additional water should be added such that water content be raised to 25%?

    125 mixture=water + other
    125 mixture=25+ 100
    for 25%
    The water is 31.25

    both are same
    25+100=31.25+93.75

    not getting it.
     
  14. tjohnson

    Active Member

    Dec 23, 2014
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    Sorry, but you won't get it unless you solve it the way I showed in post #12.
     
  15. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    125 gallons of a mixture contains 20% water.
    so, 25 gallon of water right?
    100 gallon mixture

    What amount of additional water should be added such that water content be raised to 25%?


    so,
    31.25 gallon water + 93.75 mixture right?
     
  16. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    not getting thats why.
     
  17. tjohnson

    Active Member

    Dec 23, 2014
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    No, you can't decrease the non-water part of the mixture.
     
  18. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Your answer in #8 is wrong.
    Again : If 40 is 100 %, how many percent is 10.
    10 is a quarter of 40.

    Bertus
     
  19. tjohnson

    Active Member

    Dec 23, 2014
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    Rritesh, I'm sorry to have to say this, but the solution I posted is simple algebra. I learned how to solve problems like this in Algebra 1.

    There are plenty of free resources for learning algebra like Khan Academy that you can use. Members of this forum are willing to help you, but we can't teach you all of algebra.
     
  20. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
    2,831
    89
    ok
     
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