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Finding the Fourth Proportional to 128.18, 176.78 and 78.98

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Solution

The fourth proportional to 128.18, 176.78 and 78.98 is: 108.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.18 : 176.78 = 78.98 : x
  2. Step 2: Convert to fraction form
    128.18/176.78 = 78.98/x
  3. Step 3: Cross multiply
    128.18x = 176.78 × 78.98
  4. Step 4: Simplify right side
    128.18x = 13,961.40
  5. Step 5: Solve for x
    x = 13,961.40/128.18
  6. Step 6: Final answer
    x = 108.92

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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.