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Finding the Fourth Proportional to 855.40, 1,280.40 and 828.40

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Solution

The fourth proportional to 855.40, 1,280.40 and 828.40 is: 1,239.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    855.40 : 1,280.40 = 828.40 : x
  2. Step 2: Convert to fraction form
    855.40/1,280.40 = 828.40/x
  3. Step 3: Cross multiply
    855.40x = 1,280.40 × 828.40
  4. Step 4: Simplify right side
    855.40x = 1,060,683.36
  5. Step 5: Solve for x
    x = 1,060,683.36/855.40
  6. Step 6: Final answer
    x = 1,239.99

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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.