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Finding the Fourth Proportional to 1,039.20, 1,559.16 and 390

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Solution

The fourth proportional to 1,039.20, 1,559.16 and 390 is: 585.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,039.20 : 1,559.16 = 390 : x
  2. Step 2: Convert to fraction form
    1,039.20/1,559.16 = 390/x
  3. Step 3: Cross multiply
    1,039.20x = 1,559.16 × 390
  4. Step 4: Simplify right side
    1,039.20x = 608,072.40
  5. Step 5: Solve for x
    x = 608,072.40/1,039.20
  6. Step 6: Final answer
    x = 585.14

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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.