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Finding the Fourth Proportional to 781.40, 1,172.10 and 745.40

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Solution

The fourth proportional to 781.40, 1,172.10 and 745.40 is: 1,118.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.40 : 1,172.10 = 745.40 : x
  2. Step 2: Convert to fraction form
    781.40/1,172.10 = 745.40/x
  3. Step 3: Cross multiply
    781.40x = 1,172.10 × 745.40
  4. Step 4: Simplify right side
    781.40x = 873,683.34
  5. Step 5: Solve for x
    x = 873,683.34/781.40
  6. Step 6: Final answer
    x = 1,118.10

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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.