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Finding the Fourth Proportional to 870.78, 1,306.80 and 505.20

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Solution

The fourth proportional to 870.78, 1,306.80 and 505.20 is: 758.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    870.78 : 1,306.80 = 505.20 : x
  2. Step 2: Convert to fraction form
    870.78/1,306.80 = 505.20/x
  3. Step 3: Cross multiply
    870.78x = 1,306.80 × 505.20
  4. Step 4: Simplify right side
    870.78x = 660,195.36
  5. Step 5: Solve for x
    x = 660,195.36/870.78
  6. Step 6: Final answer
    x = 758.17

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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.