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Finding the Fourth Proportional to 1,287.15, 1,928.64 and 765.90

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Solution

The fourth proportional to 1,287.15, 1,928.64 and 765.90 is: 1,147.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.15 : 1,928.64 = 765.90 : x
  2. Step 2: Convert to fraction form
    1,287.15/1,928.64 = 765.90/x
  3. Step 3: Cross multiply
    1,287.15x = 1,928.64 × 765.90
  4. Step 4: Simplify right side
    1,287.15x = 1,477,145.38
  5. Step 5: Solve for x
    x = 1,477,145.38/1,287.15
  6. Step 6: Final answer
    x = 1,147.61

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.