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Finding the Fourth Proportional to 1,139.12, 1,572 and 641.76

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Solution

The fourth proportional to 1,139.12, 1,572 and 641.76 is: 885.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,139.12 : 1,572 = 641.76 : x
  2. Step 2: Convert to fraction form
    1,139.12/1,572 = 641.76/x
  3. Step 3: Cross multiply
    1,139.12x = 1,572 × 641.76
  4. Step 4: Simplify right side
    1,139.12x = 1,008,846.72
  5. Step 5: Solve for x
    x = 1,008,846.72/1,139.12
  6. Step 6: Final answer
    x = 885.64

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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.