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Finding the Fourth Proportional to 1,139.70, 1,572.69 and 642.30

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Solution

The fourth proportional to 1,139.70, 1,572.69 and 642.30 is: 886.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,139.70 : 1,572.69 = 642.30 : x
  2. Step 2: Convert to fraction form
    1,139.70/1,572.69 = 642.30/x
  3. Step 3: Cross multiply
    1,139.70x = 1,572.69 × 642.30
  4. Step 4: Simplify right side
    1,139.70x = 1,010,138.79
  5. Step 5: Solve for x
    x = 1,010,138.79/1,139.70
  6. Step 6: Final answer
    x = 886.32

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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.