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Finding the Fourth Proportional to 390.47, 538.80 and 215.81

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Solution

The fourth proportional to 390.47, 538.80 and 215.81 is: 297.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.47 : 538.80 = 215.81 : x
  2. Step 2: Convert to fraction form
    390.47/538.80 = 215.81/x
  3. Step 3: Cross multiply
    390.47x = 538.80 × 215.81
  4. Step 4: Simplify right side
    390.47x = 116,281.19
  5. Step 5: Solve for x
    x = 116,281.19/390.47
  6. Step 6: Final answer
    x = 297.80

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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.