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Finding the Fourth Proportional to 858.40, 1,287.60 and 281.20

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Solution

The fourth proportional to 858.40, 1,287.60 and 281.20 is: 421.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    858.40 : 1,287.60 = 281.20 : x
  2. Step 2: Convert to fraction form
    858.40/1,287.60 = 281.20/x
  3. Step 3: Cross multiply
    858.40x = 1,287.60 × 281.20
  4. Step 4: Simplify right side
    858.40x = 362,073.12
  5. Step 5: Solve for x
    x = 362,073.12/858.40
  6. Step 6: Final answer
    x = 421.80

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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.