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Finding the Fourth Proportional to 100.65, 138.90 and 57

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Solution

The fourth proportional to 100.65, 138.90 and 57 is: 78.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.65 : 138.90 = 57 : x
  2. Step 2: Convert to fraction form
    100.65/138.90 = 57/x
  3. Step 3: Cross multiply
    100.65x = 138.90 × 57
  4. Step 4: Simplify right side
    100.65x = 7,917.30
  5. Step 5: Solve for x
    x = 7,917.30/100.65
  6. Step 6: Final answer
    x = 78.66

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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.