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Finding the Fourth Proportional to 720.87, 1,079.29 and 390.63

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Solution

The fourth proportional to 720.87, 1,079.29 and 390.63 is: 584.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    720.87 : 1,079.29 = 390.63 : x
  2. Step 2: Convert to fraction form
    720.87/1,079.29 = 390.63/x
  3. Step 3: Cross multiply
    720.87x = 1,079.29 × 390.63
  4. Step 4: Simplify right side
    720.87x = 421,595.70
  5. Step 5: Solve for x
    x = 421,595.70/720.87
  6. Step 6: Final answer
    x = 584.84

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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.