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Finding the Fourth Proportional to 261.39, 392.12 and 78.78

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Solution

The fourth proportional to 261.39, 392.12 and 78.78 is: 118.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.39 : 392.12 = 78.78 : x
  2. Step 2: Convert to fraction form
    261.39/392.12 = 78.78/x
  3. Step 3: Cross multiply
    261.39x = 392.12 × 78.78
  4. Step 4: Simplify right side
    261.39x = 30,890.82
  5. Step 5: Solve for x
    x = 30,890.82/261.39
  6. Step 6: Final answer
    x = 118.18

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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.