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Finding the Fourth Proportional to 989.76, 1,367.20 and 678.72

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Solution

The fourth proportional to 989.76, 1,367.20 and 678.72 is: 937.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    989.76 : 1,367.20 = 678.72 : x
  2. Step 2: Convert to fraction form
    989.76/1,367.20 = 678.72/x
  3. Step 3: Cross multiply
    989.76x = 1,367.20 × 678.72
  4. Step 4: Simplify right side
    989.76x = 927,945.98
  5. Step 5: Solve for x
    x = 927,945.98/989.76
  6. Step 6: Final answer
    x = 937.55

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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.