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Finding the Fourth Proportional to 989.58, 1,365.78 and 641.28

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Solution

The fourth proportional to 989.58, 1,365.78 and 641.28 is: 885.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    989.58 : 1,365.78 = 641.28 : x
  2. Step 2: Convert to fraction form
    989.58/1,365.78 = 641.28/x
  3. Step 3: Cross multiply
    989.58x = 1,365.78 × 641.28
  4. Step 4: Simplify right side
    989.58x = 875,847.40
  5. Step 5: Solve for x
    x = 875,847.40/989.58
  6. Step 6: Final answer
    x = 885.07

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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.