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Finding the Fourth Proportional to 861.88, 1,291.59 and 428.53

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Solution

The fourth proportional to 861.88, 1,291.59 and 428.53 is: 642.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.88 : 1,291.59 = 428.53 : x
  2. Step 2: Convert to fraction form
    861.88/1,291.59 = 428.53/x
  3. Step 3: Cross multiply
    861.88x = 1,291.59 × 428.53
  4. Step 4: Simplify right side
    861.88x = 553,485.06
  5. Step 5: Solve for x
    x = 553,485.06/861.88
  6. Step 6: Final answer
    x = 642.18

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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.