Math Problem Statement

두 수 a, b 에 대하여 합과 차의 비가 3 : 2 일 때, a / b 의 값을 x 라 하고, a - 2b = 3a - b 일 때, (a - b) / (a + b) 의 값을 y 라 한다. 이때, x + y 의 값을 구하라.

Solution

This is a mathematical problem involving two variables aa and bb, along with ratios and specific conditions to determine the values of xx and yy, ultimately finding x+yx + y.

Here’s how we interpret and solve the problem step by step:


Problem Interpretation:

  1. Conditions and Definitions:
    • a>b>0a > b > 0
    • The ratio of the sum (a+ba + b) and the difference (aba - b) is 3:23 : 2. a+bab=32\frac{a + b}{a - b} = \frac{3}{2}
    • Let ab=x\frac{a}{b} = x.
    • Another condition is given: a2b=3aba - 2b = 3a - b, and you are asked to find aba+b=y\frac{a - b}{a + b} = y.
    • Finally, find x+yx + y.

Solution Steps:

Step 1: Solve a+bab=32\frac{a + b}{a - b} = \frac{3}{2}:

From the ratio: a+bab=32\frac{a + b}{a - b} = \frac{3}{2} Cross-multiply: 2(a+b)=3(ab)2(a + b) = 3(a - b) Simplify: 2a+2b=3a3b2a + 2b = 3a - 3b a=5ba = 5b


Step 2: Find x=abx = \frac{a}{b}:

Since a=5ba = 5b, x=ab=5bb=5x = \frac{a}{b} = \frac{5b}{b} = 5


Step 3: Solve for y=aba+by = \frac{a - b}{a + b}:

Using a=5ba = 5b, ab=5bb=4b,a - b = 5b - b = 4b, a+b=5b+b=6b.a + b = 5b + b = 6b. Thus, y=aba+b=4b6b=23.y = \frac{a - b}{a + b} = \frac{4b}{6b} = \frac{2}{3}.


Step 4: Find x+yx + y:

x+y=5+23=153+23=173.x + y = 5 + \frac{2}{3} = \frac{15}{3} + \frac{2}{3} = \frac{17}{3}.


Final Answer:

x+y=173x + y = \frac{17}{3}

Would you like further clarification or additional examples on similar problems?


Related Questions:

  1. What is the derivation of the condition a2b=3aba - 2b = 3a - b?
  2. Can you calculate x+yx + y for different ratios, such as a+bab=43\frac{a+b}{a-b} = \frac{4}{3}?
  3. How do we handle the problem if a<ba < b?
  4. What happens if the ratio is not given directly but inferred from other conditions?
  5. Can xx and yy be expressed in terms of other variables if more conditions are given?

Tip:

Always simplify ratios and use substitution to solve problems with multiple conditions systematically.

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Math Problem Analysis

Mathematical Concepts

Algebra
Ratios
Substitution

Formulas

\frac{a + b}{a - b} = \frac{3}{2}
a = 5b
x = \frac{a}{b}
y = \frac{a - b}{a + b}

Theorems

Solving ratios
Algebraic substitution

Suitable Grade Level

Grade 9-10