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Finding the Fourth Proportional to 206.40, 309.54 and 90.79

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Solution

The fourth proportional to 206.40, 309.54 and 90.79 is: 136.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    206.40 : 309.54 = 90.79 : x
  2. Step 2: Convert to fraction form
    206.40/309.54 = 90.79/x
  3. Step 3: Cross multiply
    206.40x = 309.54 × 90.79
  4. Step 4: Simplify right side
    206.40x = 28,102.36
  5. Step 5: Solve for x
    x = 28,102.36/206.40
  6. Step 6: Final answer
    x = 136.15

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.