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Finding the Fourth Proportional to 877.72, 1,211.10 and 645.40

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Solution

The fourth proportional to 877.72, 1,211.10 and 645.40 is: 890.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    877.72 : 1,211.10 = 645.40 : x
  2. Step 2: Convert to fraction form
    877.72/1,211.10 = 645.40/x
  3. Step 3: Cross multiply
    877.72x = 1,211.10 × 645.40
  4. Step 4: Simplify right side
    877.72x = 781,643.94
  5. Step 5: Solve for x
    x = 781,643.94/877.72
  6. Step 6: Final answer
    x = 890.54

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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.