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Finding the Fourth Proportional to 115.38, 172.86 and 78.72

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Solution

The fourth proportional to 115.38, 172.86 and 78.72 is: 117.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    115.38 : 172.86 = 78.72 : x
  2. Step 2: Convert to fraction form
    115.38/172.86 = 78.72/x
  3. Step 3: Cross multiply
    115.38x = 172.86 × 78.72
  4. Step 4: Simplify right side
    115.38x = 13,607.54
  5. Step 5: Solve for x
    x = 13,607.54/115.38
  6. Step 6: Final answer
    x = 117.94

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.