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Finding the Fourth Proportional to 85.70, 128.36 and 42.28

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Solution

The fourth proportional to 85.70, 128.36 and 42.28 is: 63.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.70 : 128.36 = 42.28 : x
  2. Step 2: Convert to fraction form
    85.70/128.36 = 42.28/x
  3. Step 3: Cross multiply
    85.70x = 128.36 × 42.28
  4. Step 4: Simplify right side
    85.70x = 5,427.06
  5. Step 5: Solve for x
    x = 5,427.06/85.70
  6. Step 6: Final answer
    x = 63.33

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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.