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Finding the Fourth Proportional to 100.58, 138.78 and 56.91

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Solution

The fourth proportional to 100.58, 138.78 and 56.91 is: 78.53

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.58 : 138.78 = 56.91 : x
  2. Step 2: Convert to fraction form
    100.58/138.78 = 56.91/x
  3. Step 3: Cross multiply
    100.58x = 138.78 × 56.91
  4. Step 4: Simplify right side
    100.58x = 7,897.97
  5. Step 5: Solve for x
    x = 7,897.97/100.58
  6. Step 6: Final answer
    x = 78.53

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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.