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Finding the Fourth Proportional to 631, 870.78 and 355

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Solution

The fourth proportional to 631, 870.78 and 355 is: 489.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    631 : 870.78 = 355 : x
  2. Step 2: Convert to fraction form
    631/870.78 = 355/x
  3. Step 3: Cross multiply
    631x = 870.78 × 355
  4. Step 4: Simplify right side
    631x = 309,126.90
  5. Step 5: Solve for x
    x = 309,126.90/631
  6. Step 6: Final answer
    x = 489.90

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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.