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Finding the Fourth Proportional to 128.15, 176.90 and 78.38

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Solution

The fourth proportional to 128.15, 176.90 and 78.38 is: 108.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.15 : 176.90 = 78.38 : x
  2. Step 2: Convert to fraction form
    128.15/176.90 = 78.38/x
  3. Step 3: Cross multiply
    128.15x = 176.90 × 78.38
  4. Step 4: Simplify right side
    128.15x = 13,865.42
  5. Step 5: Solve for x
    x = 13,865.42/128.15
  6. Step 6: Final answer
    x = 108.20

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.