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Finding the Fourth Proportional to 128.61, 177.33 and 105.21

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Solution

The fourth proportional to 128.61, 177.33 and 105.21 is: 145.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.61 : 177.33 = 105.21 : x
  2. Step 2: Convert to fraction form
    128.61/177.33 = 105.21/x
  3. Step 3: Cross multiply
    128.61x = 177.33 × 105.21
  4. Step 4: Simplify right side
    128.61x = 18,656.89
  5. Step 5: Solve for x
    x = 18,656.89/128.61
  6. Step 6: Final answer
    x = 145.07

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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.