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Finding the Fourth Proportional to 100.92, 139.20 and 86.40

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Solution

The fourth proportional to 100.92, 139.20 and 86.40 is: 119.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.92 : 139.20 = 86.40 : x
  2. Step 2: Convert to fraction form
    100.92/139.20 = 86.40/x
  3. Step 3: Cross multiply
    100.92x = 139.20 × 86.40
  4. Step 4: Simplify right side
    100.92x = 12,026.88
  5. Step 5: Solve for x
    x = 12,026.88/100.92
  6. Step 6: Final answer
    x = 119.17

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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.