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Finding the Fourth Proportional to 1,139.60, 1,572.45 and 642.20

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Solution

The fourth proportional to 1,139.60, 1,572.45 and 642.20 is: 886.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,139.60 : 1,572.45 = 642.20 : x
  2. Step 2: Convert to fraction form
    1,139.60/1,572.45 = 642.20/x
  3. Step 3: Cross multiply
    1,139.60x = 1,572.45 × 642.20
  4. Step 4: Simplify right side
    1,139.60x = 1,009,827.39
  5. Step 5: Solve for x
    x = 1,009,827.39/1,139.60
  6. Step 6: Final answer
    x = 886.12

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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.