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Finding the Fourth Proportional to 855, 1,282.50 and 399

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Solution

The fourth proportional to 855, 1,282.50 and 399 is: 598.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    855 : 1,282.50 = 399 : x
  2. Step 2: Convert to fraction form
    855/1,282.50 = 399/x
  3. Step 3: Cross multiply
    855x = 1,282.50 × 399
  4. Step 4: Simplify right side
    855x = 511,717.50
  5. Step 5: Solve for x
    x = 511,717.50/855
  6. Step 6: Final answer
    x = 598.50

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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.