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Finding the Fourth Proportional to 431.72, 643.48 and 420.18

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Solution

The fourth proportional to 431.72, 643.48 and 420.18 is: 626.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    431.72 : 643.48 = 420.18 : x
  2. Step 2: Convert to fraction form
    431.72/643.48 = 420.18/x
  3. Step 3: Cross multiply
    431.72x = 643.48 × 420.18
  4. Step 4: Simplify right side
    431.72x = 270,377.43
  5. Step 5: Solve for x
    x = 270,377.43/431.72
  6. Step 6: Final answer
    x = 626.28

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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.