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Finding the Fourth Proportional to 978.20, 1,349.70 and 628.76

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Solution

The fourth proportional to 978.20, 1,349.70 and 628.76 is: 867.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    978.20 : 1,349.70 = 628.76 : x
  2. Step 2: Convert to fraction form
    978.20/1,349.70 = 628.76/x
  3. Step 3: Cross multiply
    978.20x = 1,349.70 × 628.76
  4. Step 4: Simplify right side
    978.20x = 848,637.37
  5. Step 5: Solve for x
    x = 848,637.37/978.20
  6. Step 6: Final answer
    x = 867.55

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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.