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Finding the Fourth Proportional to 1,139.20, 1,572 and 641.80

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Solution

The fourth proportional to 1,139.20, 1,572 and 641.80 is: 885.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,139.20 : 1,572 = 641.80 : x
  2. Step 2: Convert to fraction form
    1,139.20/1,572 = 641.80/x
  3. Step 3: Cross multiply
    1,139.20x = 1,572 × 641.80
  4. Step 4: Simplify right side
    1,139.20x = 1,008,909.60
  5. Step 5: Solve for x
    x = 1,008,909.60/1,139.20
  6. Step 6: Final answer
    x = 885.63

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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.