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Finding the Fourth Proportional to 978.50, 1,349.92 and 642.28

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Solution

The fourth proportional to 978.50, 1,349.92 and 642.28 is: 886.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    978.50 : 1,349.92 = 642.28 : x
  2. Step 2: Convert to fraction form
    978.50/1,349.92 = 642.28/x
  3. Step 3: Cross multiply
    978.50x = 1,349.92 × 642.28
  4. Step 4: Simplify right side
    978.50x = 867,026.62
  5. Step 5: Solve for x
    x = 867,026.62/978.50
  6. Step 6: Final answer
    x = 886.08

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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.