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Home Aptitude Alligation or Mixture See What Others Are Saying!
  • Question
  • Two solution of 90% and 97% purity and mixed resulting in 21 liters of mixture of 94% purity. How much is the quantity of the first solution in the resulting mixture?


  • Options
  • A. 15 litres
  • B. 12 litres
  • C. 9 litres
  • D. 6 litres

  • Correct Answer
  • 9 litres 

    Explanation

    Method 1 to solve the equation.
    Let us assume the number of liters of the 90% purity solution = A
    and the number of liters of the 97% purity solution = B.
    According to question,
    Since there are 21 liters of the solution,
    A + B = 21 ...................... (1)
    Since after mixing the two solutions the new mixture has 94% purity,
    Concentrate of A + Concentrate of B = Concentrate of (A + B)
    A x 90% + B x 94% = (A+ B) x 97%
    ? A x 90/100 + B x 97/100 = (A + B) x 94/100
    ? 90A + 97B = (A + B) x 94
    ? 90A + 97B = 94A + 94B
    ? 94A + 94B - 90A- 97B = 0
    ? 4A - 3B = 0 ........................(2)
    Multiply the 3 with Equation (1) and add with Equation (2),
    3A + 3B + 4A - 3B = 63 + 0
    ? 7A = 63
    ? A = 63/7 = 9
    Put the value of A in Equation (1) , we will get
    9 + B = 21
    B = 21 - 9
    B = 12
    The first solution would be A = 9 liters.

    Method 2 to solve the equation.
    Hit and trail method.
    94% is closer to 97% but barely meaning the mixtures will not be equal parts but will be slightly more of the higher purity. Quickly eliminate A and B. Out of the others 9 is the easy choice. If the other choices were closer to half this wouldn't work.


  • More questions

    • 1. 
      Aarti can do a piece of work in 6 days. In how many days will she complete three time of work of same type?

    • Options
    • A. 18 days
    • B. 21 days
    • C. 3 days
    • D. 6 days
    • Discuss
    • 2. 
      750.0003 ÷ 19.999 =?

    • Options
    • A. 49
    • B. 18
    • C. 22
    • D. 38
    • Discuss
    • 3. 
      105, 85, 60, 30, 0, - 45, - 90?

    • Options
    • A. 0
    • B. 85
    • C. -45
    • D. 60
    • Discuss
    • 4. 
      Let A = {1, 2, {3, 4}, 5}. Which of the following statements is true?

    • Options
    • A. {3, 4} ? A
    • B. {3, 4} ? A
    • C. 1 ? A
    • D. {1, 2, 5} ? A
    • Discuss
    • 5. 
      Two vessels A and B contains milk and water mixed in the ratio 5 : 3 and 2 : 3. When these mixtures are mixed to form a new mixture containing half milk and half water, they must be taken in the ratio ?

    • Options
    • A. 2 : 5
    • B. 3 : 5
    • C. 4 : 5
    • D. 7 : 3
    • Discuss
    • 6. 
      1, 2, 4, 8, 16, 32, 64, (...), 256?

    • Options
    • A. 148
    • B. 128
    • C. 154
    • D. 164
    • Discuss
    • 7. 
      A tree is 12 m tall and casts an an 8 m long shadow. At the same time, a flag pole caste a 100 m long shadow. How long is the flag pole?

    • Options
    • A. 150 m
    • B. 200 m
    • C. 125 m
    • D. 115 m
    • Discuss
    • 8. 
      8% of 96 =? of 1/25

    • Options
    • A. 19.2
    • B. 7.68
    • C. 1.92
    • D. None of these
    • Discuss
    • 9. A certain amount earns simple interest of Rs. 1750 after 7 years. Had the interest been 2% more, how much more interest would it have earned?

    • Options
    • A. Rs. 35
    • B. Rs. 245
    • C. Rs. 350
    • D. Cannot be determined
    • E. None of these
    • Discuss
    • 10. 
      If the hands of a clock coincide in every 65 minutes (true time), in 24 hours the clock will gain:

    • Options
    • A. 10 10 minutes. 143
    • B. 9 12 minutes. 143
    • C. 11 12 minutes. 143
    • D. 12 10 minutes. 143
    • Discuss


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