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Finding the Fourth Proportional to 938.40, 1,399.80 and 830.40

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Solution

The fourth proportional to 938.40, 1,399.80 and 830.40 is: 1,238.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    938.40 : 1,399.80 = 830.40 : x
  2. Step 2: Convert to fraction form
    938.40/1,399.80 = 830.40/x
  3. Step 3: Cross multiply
    938.40x = 1,399.80 × 830.40
  4. Step 4: Simplify right side
    938.40x = 1,162,393.92
  5. Step 5: Solve for x
    x = 1,162,393.92/938.40
  6. Step 6: Final answer
    x = 1,238.70

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.