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Finding the Fourth Proportional to 1,290.78, 1,781.33 and 731.28

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Solution

The fourth proportional to 1,290.78, 1,781.33 and 731.28 is: 1,009.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,290.78 : 1,781.33 = 731.28 : x
  2. Step 2: Convert to fraction form
    1,290.78/1,781.33 = 731.28/x
  3. Step 3: Cross multiply
    1,290.78x = 1,781.33 × 731.28
  4. Step 4: Simplify right side
    1,290.78x = 1,302,638.44
  5. Step 5: Solve for x
    x = 1,302,638.44/1,290.78
  6. Step 6: Final answer
    x = 1,009.19

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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.