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Finding the Fourth Proportional to 1,391.84, 1,920.78 and 762.40

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Solution

The fourth proportional to 1,391.84, 1,920.78 and 762.40 is: 1,052.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,391.84 : 1,920.78 = 762.40 : x
  2. Step 2: Convert to fraction form
    1,391.84/1,920.78 = 762.40/x
  3. Step 3: Cross multiply
    1,391.84x = 1,920.78 × 762.40
  4. Step 4: Simplify right side
    1,391.84x = 1,464,402.67
  5. Step 5: Solve for x
    x = 1,464,402.67/1,391.84
  6. Step 6: Final answer
    x = 1,052.13

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.