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Finding the Fourth Proportional to 390.39, 538.28 and 257.72

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Solution

The fourth proportional to 390.39, 538.28 and 257.72 is: 355.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.39 : 538.28 = 257.72 : x
  2. Step 2: Convert to fraction form
    390.39/538.28 = 257.72/x
  3. Step 3: Cross multiply
    390.39x = 538.28 × 257.72
  4. Step 4: Simplify right side
    390.39x = 138,722.51
  5. Step 5: Solve for x
    x = 138,722.51/390.39
  6. Step 6: Final answer
    x = 355.35

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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.