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Finding the Fourth Proportional to 261.35, 392.09 and 78.74

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Solution

The fourth proportional to 261.35, 392.09 and 78.74 is: 118.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.35 : 392.09 = 78.74 : x
  2. Step 2: Convert to fraction form
    261.35/392.09 = 78.74/x
  3. Step 3: Cross multiply
    261.35x = 392.09 × 78.74
  4. Step 4: Simplify right side
    261.35x = 30,870.81
  5. Step 5: Solve for x
    x = 30,870.81/261.35
  6. Step 6: Final answer
    x = 118.12

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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.