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Finding the Fourth Proportional to 858, 1,287.20 and 345

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Solution

The fourth proportional to 858, 1,287.20 and 345 is: 517.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    858 : 1,287.20 = 345 : x
  2. Step 2: Convert to fraction form
    858/1,287.20 = 345/x
  3. Step 3: Cross multiply
    858x = 1,287.20 × 345
  4. Step 4: Simplify right side
    858x = 444,084
  5. Step 5: Solve for x
    x = 444,084/858
  6. Step 6: Final answer
    x = 517.58

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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.