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Finding the Fourth Proportional to 85.76, 128.70 and 55.38

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Solution

The fourth proportional to 85.76, 128.70 and 55.38 is: 83.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.76 : 128.70 = 55.38 : x
  2. Step 2: Convert to fraction form
    85.76/128.70 = 55.38/x
  3. Step 3: Cross multiply
    85.76x = 128.70 × 55.38
  4. Step 4: Simplify right side
    85.76x = 7,127.41
  5. Step 5: Solve for x
    x = 7,127.41/85.76
  6. Step 6: Final answer
    x = 83.11

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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.