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Finding the Fourth Proportional to 986.88, 1,478.76 and 639.60

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Solution

The fourth proportional to 986.88, 1,478.76 and 639.60 is: 958.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    986.88 : 1,478.76 = 639.60 : x
  2. Step 2: Convert to fraction form
    986.88/1,478.76 = 639.60/x
  3. Step 3: Cross multiply
    986.88x = 1,478.76 × 639.60
  4. Step 4: Simplify right side
    986.88x = 945,814.90
  5. Step 5: Solve for x
    x = 945,814.90/986.88
  6. Step 6: Final answer
    x = 958.39

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.