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Finding the Fourth Proportional to 85.71, 128.58 and 30.87

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Solution

The fourth proportional to 85.71, 128.58 and 30.87 is: 46.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.71 : 128.58 = 30.87 : x
  2. Step 2: Convert to fraction form
    85.71/128.58 = 30.87/x
  3. Step 3: Cross multiply
    85.71x = 128.58 × 30.87
  4. Step 4: Simplify right side
    85.71x = 3,969.26
  5. Step 5: Solve for x
    x = 3,969.26/85.71
  6. Step 6: Final answer
    x = 46.31

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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.