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Finding the Fourth Proportional to 390.65, 539.65 and 312.49

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Solution

The fourth proportional to 390.65, 539.65 and 312.49 is: 431.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.65 : 539.65 = 312.49 : x
  2. Step 2: Convert to fraction form
    390.65/539.65 = 312.49/x
  3. Step 3: Cross multiply
    390.65x = 539.65 × 312.49
  4. Step 4: Simplify right side
    390.65x = 168,632.53
  5. Step 5: Solve for x
    x = 168,632.53/390.65
  6. Step 6: Final answer
    x = 431.67

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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.