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Finding the Fourth Proportional to 1,121.45, 1,681.71 and 428.37

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Solution

The fourth proportional to 1,121.45, 1,681.71 and 428.37 is: 642.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.45 : 1,681.71 = 428.37 : x
  2. Step 2: Convert to fraction form
    1,121.45/1,681.71 = 428.37/x
  3. Step 3: Cross multiply
    1,121.45x = 1,681.71 × 428.37
  4. Step 4: Simplify right side
    1,121.45x = 720,394.11
  5. Step 5: Solve for x
    x = 720,394.11/1,121.45
  6. Step 6: Final answer
    x = 642.38

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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.