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Finding the Fourth Proportional to 390, 538.20 and 215.35

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Solution

The fourth proportional to 390, 538.20 and 215.35 is: 297.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    390 : 538.20 = 215.35 : x
  2. Step 2: Convert to fraction form
    390/538.20 = 215.35/x
  3. Step 3: Cross multiply
    390x = 538.20 × 215.35
  4. Step 4: Simplify right side
    390x = 115,900.02
  5. Step 5: Solve for x
    x = 115,900.02/390
  6. Step 6: Final answer
    x = 297.18

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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.