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Finding the Fourth Proportional to 100.45, 138.61 and 56.79

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Solution

The fourth proportional to 100.45, 138.61 and 56.79 is: 78.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.45 : 138.61 = 56.79 : x
  2. Step 2: Convert to fraction form
    100.45/138.61 = 56.79/x
  3. Step 3: Cross multiply
    100.45x = 138.61 × 56.79
  4. Step 4: Simplify right side
    100.45x = 7,871.66
  5. Step 5: Solve for x
    x = 7,871.66/100.45
  6. Step 6: Final answer
    x = 78.36

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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.