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Finding the Fourth Proportional to 261.13, 391.65 and 98.78

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Solution

The fourth proportional to 261.13, 391.65 and 98.78 is: 148.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.13 : 391.65 = 98.78 : x
  2. Step 2: Convert to fraction form
    261.13/391.65 = 98.78/x
  3. Step 3: Cross multiply
    261.13x = 391.65 × 98.78
  4. Step 4: Simplify right side
    261.13x = 38,687.19
  5. Step 5: Solve for x
    x = 38,687.19/261.13
  6. Step 6: Final answer
    x = 148.15

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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.