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Finding the Fourth Proportional to 1,113.78, 1,669.86 and 921

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Solution

The fourth proportional to 1,113.78, 1,669.86 and 921 is: 1,380.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,113.78 : 1,669.86 = 921 : x
  2. Step 2: Convert to fraction form
    1,113.78/1,669.86 = 921/x
  3. Step 3: Cross multiply
    1,113.78x = 1,669.86 × 921
  4. Step 4: Simplify right side
    1,113.78x = 1,537,941.06
  5. Step 5: Solve for x
    x = 1,537,941.06/1,113.78
  6. Step 6: Final answer
    x = 1,380.83

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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.