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Finding the Fourth Proportional to 860.78, 1,291.20 and 312.86

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Solution

The fourth proportional to 860.78, 1,291.20 and 312.86 is: 469.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    860.78 : 1,291.20 = 312.86 : x
  2. Step 2: Convert to fraction form
    860.78/1,291.20 = 312.86/x
  3. Step 3: Cross multiply
    860.78x = 1,291.20 × 312.86
  4. Step 4: Simplify right side
    860.78x = 403,964.83
  5. Step 5: Solve for x
    x = 403,964.83/860.78
  6. Step 6: Final answer
    x = 469.30

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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.