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Finding the Fourth Proportional to 427.60, 641.40 and 421.20

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Solution

The fourth proportional to 427.60, 641.40 and 421.20 is: 631.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    427.60 : 641.40 = 421.20 : x
  2. Step 2: Convert to fraction form
    427.60/641.40 = 421.20/x
  3. Step 3: Cross multiply
    427.60x = 641.40 × 421.20
  4. Step 4: Simplify right side
    427.60x = 270,157.68
  5. Step 5: Solve for x
    x = 270,157.68/427.60
  6. Step 6: Final answer
    x = 631.80

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.