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Finding the Fourth Proportional to 421.40, 631.20 and 421.40

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Solution

The fourth proportional to 421.40, 631.20 and 421.40 is: 631.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.40 : 631.20 = 421.40 : x
  2. Step 2: Convert to fraction form
    421.40/631.20 = 421.40/x
  3. Step 3: Cross multiply
    421.40x = 631.20 × 421.40
  4. Step 4: Simplify right side
    421.40x = 265,987.68
  5. Step 5: Solve for x
    x = 265,987.68/421.40
  6. Step 6: Final answer
    x = 631.20

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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.