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Finding the Fourth Proportional to 100.78, 139.06 and 57.11

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Solution

The fourth proportional to 100.78, 139.06 and 57.11 is: 78.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.78 : 139.06 = 57.11 : x
  2. Step 2: Convert to fraction form
    100.78/139.06 = 57.11/x
  3. Step 3: Cross multiply
    100.78x = 139.06 × 57.11
  4. Step 4: Simplify right side
    100.78x = 7,941.72
  5. Step 5: Solve for x
    x = 7,941.72/100.78
  6. Step 6: Final answer
    x = 78.80

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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.