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Finding the Fourth Proportional to 780.80, 1,172.12 and 415.76

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Solution

The fourth proportional to 780.80, 1,172.12 and 415.76 is: 624.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    780.80 : 1,172.12 = 415.76 : x
  2. Step 2: Convert to fraction form
    780.80/1,172.12 = 415.76/x
  3. Step 3: Cross multiply
    780.80x = 1,172.12 × 415.76
  4. Step 4: Simplify right side
    780.80x = 487,320.61
  5. Step 5: Solve for x
    x = 487,320.61/780.80
  6. Step 6: Final answer
    x = 624.13

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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.