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Finding the Fourth Proportional to 1,420.31, 2,129.73 and 639.64

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Solution

The fourth proportional to 1,420.31, 2,129.73 and 639.64 is: 959.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,420.31 : 2,129.73 = 639.64 : x
  2. Step 2: Convert to fraction form
    1,420.31/2,129.73 = 639.64/x
  3. Step 3: Cross multiply
    1,420.31x = 2,129.73 × 639.64
  4. Step 4: Simplify right side
    1,420.31x = 1,362,260.76
  5. Step 5: Solve for x
    x = 1,362,260.76/1,420.31
  6. Step 6: Final answer
    x = 959.13

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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.