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Finding the Fourth Proportional to 261.11, 391.67 and 78.51

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Solution

The fourth proportional to 261.11, 391.67 and 78.51 is: 117.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.11 : 391.67 = 78.51 : x
  2. Step 2: Convert to fraction form
    261.11/391.67 = 78.51/x
  3. Step 3: Cross multiply
    261.11x = 391.67 × 78.51
  4. Step 4: Simplify right side
    261.11x = 30,748.67
  5. Step 5: Solve for x
    x = 30,748.67/261.11
  6. Step 6: Final answer
    x = 117.76

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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.