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Finding the Fourth Proportional to 100.57, 138.74 and 56.90

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Solution

The fourth proportional to 100.57, 138.74 and 56.90 is: 78.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.57 : 138.74 = 56.90 : x
  2. Step 2: Convert to fraction form
    100.57/138.74 = 56.90/x
  3. Step 3: Cross multiply
    100.57x = 138.74 × 56.90
  4. Step 4: Simplify right side
    100.57x = 7,894.31
  5. Step 5: Solve for x
    x = 7,894.31/100.57
  6. Step 6: Final answer
    x = 78.50

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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.