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Finding the Fourth Proportional to 1,290.24, 1,780 and 765.76

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Solution

The fourth proportional to 1,290.24, 1,780 and 765.76 is: 1,056.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,290.24 : 1,780 = 765.76 : x
  2. Step 2: Convert to fraction form
    1,290.24/1,780 = 765.76/x
  3. Step 3: Cross multiply
    1,290.24x = 1,780 × 765.76
  4. Step 4: Simplify right side
    1,290.24x = 1,363,052.80
  5. Step 5: Solve for x
    x = 1,363,052.80/1,290.24
  6. Step 6: Final answer
    x = 1,056.43

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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.