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Finding the Fourth Proportional to 100.31, 138.40 and 56.64

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Solution

The fourth proportional to 100.31, 138.40 and 56.64 is: 78.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.31 : 138.40 = 56.64 : x
  2. Step 2: Convert to fraction form
    100.31/138.40 = 56.64/x
  3. Step 3: Cross multiply
    100.31x = 138.40 × 56.64
  4. Step 4: Simplify right side
    100.31x = 7,838.98
  5. Step 5: Solve for x
    x = 7,838.98/100.31
  6. Step 6: Final answer
    x = 78.15

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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.