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Finding the Fourth Proportional to 128.40, 177.17 and 79.31

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Solution

The fourth proportional to 128.40, 177.17 and 79.31 is: 109.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.40 : 177.17 = 79.31 : x
  2. Step 2: Convert to fraction form
    128.40/177.17 = 79.31/x
  3. Step 3: Cross multiply
    128.40x = 177.17 × 79.31
  4. Step 4: Simplify right side
    128.40x = 14,050.07
  5. Step 5: Solve for x
    x = 14,050.07/128.40
  6. Step 6: Final answer
    x = 109.42

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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.