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Finding the Fourth Proportional to 1,290.85, 1,781.63 and 766.78

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Solution

The fourth proportional to 1,290.85, 1,781.63 and 766.78 is: 1,058.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,290.85 : 1,781.63 = 766.78 : x
  2. Step 2: Convert to fraction form
    1,290.85/1,781.63 = 766.78/x
  3. Step 3: Cross multiply
    1,290.85x = 1,781.63 × 766.78
  4. Step 4: Simplify right side
    1,290.85x = 1,366,113.80
  5. Step 5: Solve for x
    x = 1,366,113.80/1,290.85
  6. Step 6: Final answer
    x = 1,058.31

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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.