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Question

If 5x/3 – 7/2(2x/5 – 1/3) = 1/3, then the value of x is ____.

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is

-25/8

Solving the Given Linear Equation

We are asked to find the value of \(x\) in the linear equation:

\(\frac{5x}{3} - \frac{7}{2}\left(\frac{2x}{5} - \frac{1}{3}\right) = \frac{1}{3}\)

To solve this equation for \(x\), we need to simplify it by removing the parentheses and combining like terms. Let's break down the process into several steps.

Step-by-Step Method to Find the Value of x

Here is how we can solve this linear equation:

  1. Simplify the expression inside the parentheses:
  2. First, distribute the \(\frac{7}{2}\) to both terms inside the parentheses:
  3. \(\frac{7}{2}\left(\frac{2x}{5} - \frac{1}{3}\right) = \left(\frac{7}{2} \times \frac{2x}{5}\right) - \left(\frac{7}{2} \times \frac{1}{3}\right)\)
  4. \(= \frac{14x}{10} - \frac{7}{6}\)
  5. Simplify the fraction \(\frac{14x}{10}\):
  6. \(\frac{14x}{10} = \frac{7x}{5}\)
  7. So the simplified expression is \(\frac{7x}{5} - \frac{7}{6}\).
  8. Substitute the simplified expression back into the original equation:
  9. The equation becomes:
  10. \(\frac{5x}{3} - \left(\frac{7x}{5} - \frac{7}{6}\right) = \frac{1}{3}\)
  11. Be careful with the minus sign before the parentheses. Distribute the minus sign:
  12. \(\frac{5x}{3} - \frac{7x}{5} + \frac{7}{6} = \frac{1}{3}\)
  13. Isolate terms with \(x\) on one side and constant terms on the other:
  14. Subtract \(\frac{7}{6}\) from both sides of the equation:
  15. \(\frac{5x}{3} - \frac{7x}{5} = \frac{1}{3} - \frac{7}{6}\)
  16. Combine the terms with \(x\):
  17. Find a common denominator for \(\frac{5x}{3}\) and \(\frac{7x}{5}\). The least common multiple (LCM) of 3 and 5 is 15.
  18. \(\frac{5x}{3} = \frac{5x \times 5}{3 \times 5} = \frac{25x}{15}\)
  19. \(\frac{7x}{5} = \frac{7x \times 3}{5 \times 3} = \frac{21x}{15}\)
  20. Now combine them:
  21. \(\frac{25x}{15} - \frac{21x}{15} = \frac{25x - 21x}{15} = \frac{4x}{15}\)
  22. So the left side of the equation is \(\frac{4x}{15}\).
  23. Combine the constant terms on the right side:
  24. Find a common denominator for \(\frac{1}{3}\) and \(\frac{7}{6}\). The LCM of 3 and 6 is 6.
  25. \(\frac{1}{3} = \frac{1 \times 2}{3 \times 2} = \frac{2}{6}\)
  26. Now combine them:
  27. \(\frac{2}{6} - \frac{7}{6} = \frac{2 - 7}{6} = \frac{-5}{6}\)
  28. So the right side of the equation is \(\frac{-5}{6}\).
  29. Equate the simplified sides and solve for \(x\):
  30. The equation is now:
  31. \(\frac{4x}{15} = \frac{-5}{6}\)
  32. To isolate \(x\), multiply both sides by 15:
  33. \(4x = \frac{-5}{6} \times 15\)
  34. \(4x = \frac{-75}{6}\)
  35. Simplify the fraction \(\frac{-75}{6}\) by dividing the numerator and denominator by their greatest common divisor, which is 3:
  36. \(\frac{-75 \div 3}{6 \div 3} = \frac{-25}{2}\)
  37. So, \(4x = \frac{-25}{2}\).
  38. Now, divide both sides by 4:
  39. \(x = \frac{-25}{2} \div 4\)
  40. \(x = \frac{-25}{2} \times \frac{1}{4}\)
  41. \(x = \frac{-25 \times 1}{2 \times 4}\)
  42. \(x = \frac{-25}{8}\)

Thus, the value of \(x\) that satisfies the given equation is \(\frac{-25}{8}\).

Revision Table: Steps to Solve Linear Equations

Step Description Action in this problem
1 Simplify by removing parentheses (distribute) Distribute \(-\frac{7}{2}\) in \(-\frac{7}{2}(\frac{2x}{5} - \frac{1}{3})\)
2 Combine like terms on each side (if any) No like terms on either side initially after distribution
3 Move terms with variable to one side, constants to the other Move \(\frac{7}{6}\) to the right side
4 Combine variable terms and constant terms Combine \(\frac{5x}{3} - \frac{7x}{5}\) and \(\frac{1}{3} - \frac{7}{6}\) using common denominators
5 Solve for the variable Isolate \(x\) by multiplying by the reciprocal of its coefficient

Additional Information on Solving Algebraic Equations

Solving linear equations involves isolating the variable using inverse operations. Key concepts include:

  • Distributive Property: \(a(b+c) = ab + ac\). This is used to remove parentheses.
  • Combining Like Terms: Terms with the same variable raised to the same power (or constant terms) can be added or subtracted.
  • Properties of Equality:
    • Addition Property: Adding the same number to both sides of an equation keeps the equation balanced.
    • Subtraction Property: Subtracting the same number from both sides keeps the equation balanced.
    • Multiplication Property: Multiplying both sides by the same non-zero number keeps the equation balanced.
    • Division Property: Dividing both sides by the same non-zero number keeps the equation balanced.
  • Least Common Multiple (LCM): Used to find a common denominator when adding or subtracting fractions. Multiplying the entire equation by the LCM of all denominators can clear the fractions, making the equation easier to solve. In step 6 above, instead of combining fractions first, we could have multiplied the entire equation \(\frac{5x}{3} - \frac{7x}{5} + \frac{7}{6} = \frac{1}{3}\) by the LCM of 3, 5, and 6 (which is 30) to clear the denominators.
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Important Questions from Linear Equation in 1 Variable

  1. A man has equal number of five, ten and twenty rupee notes amounting to Rs. 385. Find the total number of notes?

  2. The sum of three consecutive number is 126. Find the highest number?

  3. Simplify 5x(x + 2) + 4x

    A.5x 2+ 10

    B.9x + 10

    C.5x 2- 14x

    D.5x 2+ 14x
  4. Solve:

    x - 4 = -3

    A. 7

    B. -1

    C. -7

    D. 1

  5. If 4(3x - 2) = 2(3x + 8), Then x = ?

    A. 1

    B. 2

    C. 3

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