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Finding the Fourth Proportional to 390.59, 538.99 and 215.90

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Solution

The fourth proportional to 390.59, 538.99 and 215.90 is: 297.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.59 : 538.99 = 215.90 : x
  2. Step 2: Convert to fraction form
    390.59/538.99 = 215.90/x
  3. Step 3: Cross multiply
    390.59x = 538.99 × 215.90
  4. Step 4: Simplify right side
    390.59x = 116,364.71
  5. Step 5: Solve for x
    x = 116,364.71/390.59
  6. Step 6: Final answer
    x = 297.92

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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.