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Finding the Fourth Proportional to 100.39, 138.54 and 56.74

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Solution

The fourth proportional to 100.39, 138.54 and 56.74 is: 78.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.39 : 138.54 = 56.74 : x
  2. Step 2: Convert to fraction form
    100.39/138.54 = 56.74/x
  3. Step 3: Cross multiply
    100.39x = 138.54 × 56.74
  4. Step 4: Simplify right side
    100.39x = 7,860.76
  5. Step 5: Solve for x
    x = 7,860.76/100.39
  6. Step 6: Final answer
    x = 78.30

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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.