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Finding the Fourth Proportional to 1,139.76, 1,572.85 and 642.40

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Solution

The fourth proportional to 1,139.76, 1,572.85 and 642.40 is: 886.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,139.76 : 1,572.85 = 642.40 : x
  2. Step 2: Convert to fraction form
    1,139.76/1,572.85 = 642.40/x
  3. Step 3: Cross multiply
    1,139.76x = 1,572.85 × 642.40
  4. Step 4: Simplify right side
    1,139.76x = 1,010,398.84
  5. Step 5: Solve for x
    x = 1,010,398.84/1,139.76
  6. Step 6: Final answer
    x = 886.50

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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.