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Finding the Fourth Proportional to 998.90, 1,378.05 and 687.86

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Solution

The fourth proportional to 998.90, 1,378.05 and 687.86 is: 948.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    998.90 : 1,378.05 = 687.86 : x
  2. Step 2: Convert to fraction form
    998.90/1,378.05 = 687.86/x
  3. Step 3: Cross multiply
    998.90x = 1,378.05 × 687.86
  4. Step 4: Simplify right side
    998.90x = 947,905.47
  5. Step 5: Solve for x
    x = 947,905.47/998.90
  6. Step 6: Final answer
    x = 948.95

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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.