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Finding the Fourth Proportional to 781.60, 1,172.40 and 721.60

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Solution

The fourth proportional to 781.60, 1,172.40 and 721.60 is: 1,082.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.60 : 1,172.40 = 721.60 : x
  2. Step 2: Convert to fraction form
    781.60/1,172.40 = 721.60/x
  3. Step 3: Cross multiply
    781.60x = 1,172.40 × 721.60
  4. Step 4: Simplify right side
    781.60x = 846,003.84
  5. Step 5: Solve for x
    x = 846,003.84/781.60
  6. Step 6: Final answer
    x = 1,082.40

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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.