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Finding the Fourth Proportional to 671.40, 1,005.21 and 427.32

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Solution

The fourth proportional to 671.40, 1,005.21 and 427.32 is: 639.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    671.40 : 1,005.21 = 427.32 : x
  2. Step 2: Convert to fraction form
    671.40/1,005.21 = 427.32/x
  3. Step 3: Cross multiply
    671.40x = 1,005.21 × 427.32
  4. Step 4: Simplify right side
    671.40x = 429,546.34
  5. Step 5: Solve for x
    x = 429,546.34/671.40
  6. Step 6: Final answer
    x = 639.78

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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.