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Finding the Fourth Proportional to 100.12, 138.15 and 56.45

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Solution

The fourth proportional to 100.12, 138.15 and 56.45 is: 77.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.12 : 138.15 = 56.45 : x
  2. Step 2: Convert to fraction form
    100.12/138.15 = 56.45/x
  3. Step 3: Cross multiply
    100.12x = 138.15 × 56.45
  4. Step 4: Simplify right side
    100.12x = 7,798.57
  5. Step 5: Solve for x
    x = 7,798.57/100.12
  6. Step 6: Final answer
    x = 77.89

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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.