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Finding the Fourth Proportional to 685.75, 946.47 and 391

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Solution

The fourth proportional to 685.75, 946.47 and 391 is: 539.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.75 : 946.47 = 391 : x
  2. Step 2: Convert to fraction form
    685.75/946.47 = 391/x
  3. Step 3: Cross multiply
    685.75x = 946.47 × 391
  4. Step 4: Simplify right side
    685.75x = 370,069.77
  5. Step 5: Solve for x
    x = 370,069.77/685.75
  6. Step 6: Final answer
    x = 539.66

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.