Three-fourths of a number exceeds two-thirds of the same number by 5. What is the number?

Difficulty: Easy

Correct Answer: 60

Explanation:


Introduction / Context:
This is another linear equation built from the difference of two fractional parts of a number. Solving requires careful fraction subtraction and then isolating the unknown. It checks comfort with least common multiples and proportional reasoning.


Given Data / Assumptions:

  • (3/4)N − (2/3)N = 5.
  • N is real and positive.
  • We must find N.


Concept / Approach:
Subtract the fractions with a common denominator, then equate the result to 5 and solve for N. Using the identity (a/b − c/d) = (ad − bc) / bd helps to avoid errors.


Step-by-Step Solution:

Compute the difference: 3/4 − 2/3 = (9/12 − 8/12) = 1/12.Set the equation: (1/12) * N = 5.Solve: N = 5 * 12 = 60.Therefore, the required number is 60.


Verification / Alternative check:
Check: (3/4)*60 = 45; (2/3)*60 = 40; 45 − 40 = 5. The condition holds perfectly.


Why Other Options Are Wrong:
48, 72, 84, and 36 yield differences other than 5 when substituted into the expression (3/4)N − (2/3)N.


Common Pitfalls:
Computing 3/4 − 2/3 incorrectly (e.g., 1/12 reversed in sign) or multiplying by the wrong reciprocal when isolating N.


Final Answer:
60

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