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Finding the Fourth Proportional to 820.40, 1,231.20 and 612.64

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Solution

The fourth proportional to 820.40, 1,231.20 and 612.64 is: 919.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    820.40 : 1,231.20 = 612.64 : x
  2. Step 2: Convert to fraction form
    820.40/1,231.20 = 612.64/x
  3. Step 3: Cross multiply
    820.40x = 1,231.20 × 612.64
  4. Step 4: Simplify right side
    820.40x = 754,282.37
  5. Step 5: Solve for x
    x = 754,282.37/820.40
  6. Step 6: Final answer
    x = 919.41

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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.