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Finding the Fourth Proportional to 1,408.68, 2,113.56 and 639

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Solution

The fourth proportional to 1,408.68, 2,113.56 and 639 is: 958.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,408.68 : 2,113.56 = 639 : x
  2. Step 2: Convert to fraction form
    1,408.68/2,113.56 = 639/x
  3. Step 3: Cross multiply
    1,408.68x = 2,113.56 × 639
  4. Step 4: Simplify right side
    1,408.68x = 1,350,564.84
  5. Step 5: Solve for x
    x = 1,350,564.84/1,408.68
  6. Step 6: Final answer
    x = 958.74

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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.