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Finding the Fourth Proportional to 390.42, 538.78 and 215.76

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Solution

The fourth proportional to 390.42, 538.78 and 215.76 is: 297.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.42 : 538.78 = 215.76 : x
  2. Step 2: Convert to fraction form
    390.42/538.78 = 215.76/x
  3. Step 3: Cross multiply
    390.42x = 538.78 × 215.76
  4. Step 4: Simplify right side
    390.42x = 116,247.17
  5. Step 5: Solve for x
    x = 116,247.17/390.42
  6. Step 6: Final answer
    x = 297.75

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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.