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Finding the Fourth Proportional to 639.90, 960.75 and 420.57

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Solution

The fourth proportional to 639.90, 960.75 and 420.57 is: 631.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.90 : 960.75 = 420.57 : x
  2. Step 2: Convert to fraction form
    639.90/960.75 = 420.57/x
  3. Step 3: Cross multiply
    639.90x = 960.75 × 420.57
  4. Step 4: Simplify right side
    639.90x = 404,062.63
  5. Step 5: Solve for x
    x = 404,062.63/639.90
  6. Step 6: Final answer
    x = 631.45

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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.