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Finding the Fourth Proportional to 128.56, 176.94 and 99.40

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Solution

The fourth proportional to 128.56, 176.94 and 99.40 is: 136.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.56 : 176.94 = 99.40 : x
  2. Step 2: Convert to fraction form
    128.56/176.94 = 99.40/x
  3. Step 3: Cross multiply
    128.56x = 176.94 × 99.40
  4. Step 4: Simplify right side
    128.56x = 17,587.84
  5. Step 5: Solve for x
    x = 17,587.84/128.56
  6. Step 6: Final answer
    x = 136.81

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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.