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Finding the Fourth Proportional to 128.20, 177 and 79.12

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Solution

The fourth proportional to 128.20, 177 and 79.12 is: 109.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.20 : 177 = 79.12 : x
  2. Step 2: Convert to fraction form
    128.20/177 = 79.12/x
  3. Step 3: Cross multiply
    128.20x = 177 × 79.12
  4. Step 4: Simplify right side
    128.20x = 14,004.24
  5. Step 5: Solve for x
    x = 14,004.24/128.20
  6. Step 6: Final answer
    x = 109.24

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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.