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Finding the Fourth Proportional to 85.43, 128 and 39.77

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Solution

The fourth proportional to 85.43, 128 and 39.77 is: 59.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.43 : 128 = 39.77 : x
  2. Step 2: Convert to fraction form
    85.43/128 = 39.77/x
  3. Step 3: Cross multiply
    85.43x = 128 × 39.77
  4. Step 4: Simplify right side
    85.43x = 5,089.92
  5. Step 5: Solve for x
    x = 5,089.92/85.43
  6. Step 6: Final answer
    x = 59.58

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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.