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Finding the Fourth Proportional to 989.92, 1,364.70 and 640

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Solution

The fourth proportional to 989.92, 1,364.70 and 640 is: 882.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    989.92 : 1,364.70 = 640 : x
  2. Step 2: Convert to fraction form
    989.92/1,364.70 = 640/x
  3. Step 3: Cross multiply
    989.92x = 1,364.70 × 640
  4. Step 4: Simplify right side
    989.92x = 873,408
  5. Step 5: Solve for x
    x = 873,408/989.92
  6. Step 6: Final answer
    x = 882.30

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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.