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Finding the Fourth Proportional to 687.40, 1,028.70 and 629.80

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Solution

The fourth proportional to 687.40, 1,028.70 and 629.80 is: 942.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.40 : 1,028.70 = 629.80 : x
  2. Step 2: Convert to fraction form
    687.40/1,028.70 = 629.80/x
  3. Step 3: Cross multiply
    687.40x = 1,028.70 × 629.80
  4. Step 4: Simplify right side
    687.40x = 647,875.26
  5. Step 5: Solve for x
    x = 647,875.26/687.40
  6. Step 6: Final answer
    x = 942.50

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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.