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Finding the Fourth Proportional to 390.48, 539.64 and 312.72

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Solution

The fourth proportional to 390.48, 539.64 and 312.72 is: 432.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.48 : 539.64 = 312.72 : x
  2. Step 2: Convert to fraction form
    390.48/539.64 = 312.72/x
  3. Step 3: Cross multiply
    390.48x = 539.64 × 312.72
  4. Step 4: Simplify right side
    390.48x = 168,756.22
  5. Step 5: Solve for x
    x = 168,756.22/390.48
  6. Step 6: Final answer
    x = 432.18

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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.