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Finding the Fourth Proportional to 1,311.05, 1,809.28 and 780.00

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Solution

The fourth proportional to 1,311.05, 1,809.28 and 780.00 is: 1,076.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,311.05 : 1,809.28 = 780.00 : x
  2. Step 2: Convert to fraction form
    1,311.05/1,809.28 = 780.00/x
  3. Step 3: Cross multiply
    1,311.05x = 1,809.28 × 780.00
  4. Step 4: Simplify right side
    1,311.05x = 1,411,229.35
  5. Step 5: Solve for x
    x = 1,411,229.35/1,311.05
  6. Step 6: Final answer
    x = 1,076.41

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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.