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Finding the Fourth Proportional to 85.57, 128.18 and 70.31

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Solution

The fourth proportional to 85.57, 128.18 and 70.31 is: 105.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.57 : 128.18 = 70.31 : x
  2. Step 2: Convert to fraction form
    85.57/128.18 = 70.31/x
  3. Step 3: Cross multiply
    85.57x = 128.18 × 70.31
  4. Step 4: Simplify right side
    85.57x = 9,011.69
  5. Step 5: Solve for x
    x = 9,011.69/85.57
  6. Step 6: Final answer
    x = 105.31

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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.