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Finding the Fourth Proportional to 1,121.79, 1,683.17 and 428.67

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Solution

The fourth proportional to 1,121.79, 1,683.17 and 428.67 is: 643.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.79 : 1,683.17 = 428.67 : x
  2. Step 2: Convert to fraction form
    1,121.79/1,683.17 = 428.67/x
  3. Step 3: Cross multiply
    1,121.79x = 1,683.17 × 428.67
  4. Step 4: Simplify right side
    1,121.79x = 721,513.92
  5. Step 5: Solve for x
    x = 721,513.92/1,121.79
  6. Step 6: Final answer
    x = 643.18

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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.