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Finding the Fourth Proportional to 390.80, 539.50 and 258.20

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Solution

The fourth proportional to 390.80, 539.50 and 258.20 is: 356.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.80 : 539.50 = 258.20 : x
  2. Step 2: Convert to fraction form
    390.80/539.50 = 258.20/x
  3. Step 3: Cross multiply
    390.80x = 539.50 × 258.20
  4. Step 4: Simplify right side
    390.80x = 139,298.90
  5. Step 5: Solve for x
    x = 139,298.90/390.80
  6. Step 6: Final answer
    x = 356.45

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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.