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Finding the Fourth Proportional to 405.18, 559.71 and 390.20

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Solution

The fourth proportional to 405.18, 559.71 and 390.20 is: 539.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    405.18 : 559.71 = 390.20 : x
  2. Step 2: Convert to fraction form
    405.18/559.71 = 390.20/x
  3. Step 3: Cross multiply
    405.18x = 559.71 × 390.20
  4. Step 4: Simplify right side
    405.18x = 218,398.84
  5. Step 5: Solve for x
    x = 218,398.84/405.18
  6. Step 6: Final answer
    x = 539.02

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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.