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Finding the Fourth Proportional to 390.45, 538.80 and 215.79

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Solution

The fourth proportional to 390.45, 538.80 and 215.79 is: 297.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.45 : 538.80 = 215.79 : x
  2. Step 2: Convert to fraction form
    390.45/538.80 = 215.79/x
  3. Step 3: Cross multiply
    390.45x = 538.80 × 215.79
  4. Step 4: Simplify right side
    390.45x = 116,267.65
  5. Step 5: Solve for x
    x = 116,267.65/390.45
  6. Step 6: Final answer
    x = 297.78

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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.