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Finding the Fourth Proportional to 128.56, 177.38 and 81.90

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Solution

The fourth proportional to 128.56, 177.38 and 81.90 is: 113.00

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.56 : 177.38 = 81.90 : x
  2. Step 2: Convert to fraction form
    128.56/177.38 = 81.90/x
  3. Step 3: Cross multiply
    128.56x = 177.38 × 81.90
  4. Step 4: Simplify right side
    128.56x = 14,527.42
  5. Step 5: Solve for x
    x = 14,527.42/128.56
  6. Step 6: Final answer
    x = 113.00

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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.