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Finding the Fourth Proportional to 109.78, 151.47 and 81.40

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Solution

The fourth proportional to 109.78, 151.47 and 81.40 is: 112.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    109.78 : 151.47 = 81.40 : x
  2. Step 2: Convert to fraction form
    109.78/151.47 = 81.40/x
  3. Step 3: Cross multiply
    109.78x = 151.47 × 81.40
  4. Step 4: Simplify right side
    109.78x = 12,329.66
  5. Step 5: Solve for x
    x = 12,329.66/109.78
  6. Step 6: Final answer
    x = 112.31

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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.