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Finding the Fourth Proportional to 930.40, 1,395.60 and 638.80

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Solution

The fourth proportional to 930.40, 1,395.60 and 638.80 is: 958.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    930.40 : 1,395.60 = 638.80 : x
  2. Step 2: Convert to fraction form
    930.40/1,395.60 = 638.80/x
  3. Step 3: Cross multiply
    930.40x = 1,395.60 × 638.80
  4. Step 4: Simplify right side
    930.40x = 891,509.28
  5. Step 5: Solve for x
    x = 891,509.28/930.40
  6. Step 6: Final answer
    x = 958.20

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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.