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Finding the Fourth Proportional to 92.78, 128.04 and 76.40

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Solution

The fourth proportional to 92.78, 128.04 and 76.40 is: 105.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    92.78 : 128.04 = 76.40 : x
  2. Step 2: Convert to fraction form
    92.78/128.04 = 76.40/x
  3. Step 3: Cross multiply
    92.78x = 128.04 × 76.40
  4. Step 4: Simplify right side
    92.78x = 9,782.26
  5. Step 5: Solve for x
    x = 9,782.26/92.78
  6. Step 6: Final answer
    x = 105.43

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.