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Finding the Fourth Proportional to 421.32, 628 and 390.16

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Solution

The fourth proportional to 421.32, 628 and 390.16 is: 581.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.32 : 628 = 390.16 : x
  2. Step 2: Convert to fraction form
    421.32/628 = 390.16/x
  3. Step 3: Cross multiply
    421.32x = 628 × 390.16
  4. Step 4: Simplify right side
    421.32x = 245,020.48
  5. Step 5: Solve for x
    x = 245,020.48/421.32
  6. Step 6: Final answer
    x = 581.55

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.