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Finding the Fourth Proportional to 1,289, 1,778.06 and 765

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Solution

The fourth proportional to 1,289, 1,778.06 and 765 is: 1,055.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,289 : 1,778.06 = 765 : x
  2. Step 2: Convert to fraction form
    1,289/1,778.06 = 765/x
  3. Step 3: Cross multiply
    1,289x = 1,778.06 × 765
  4. Step 4: Simplify right side
    1,289x = 1,360,215.90
  5. Step 5: Solve for x
    x = 1,360,215.90/1,289
  6. Step 6: Final answer
    x = 1,055.25

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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.