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Finding the Fourth Proportional to 1,287.80, 1,931.88 and 422

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Solution

The fourth proportional to 1,287.80, 1,931.88 and 422 is: 633.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.80 : 1,931.88 = 422 : x
  2. Step 2: Convert to fraction form
    1,287.80/1,931.88 = 422/x
  3. Step 3: Cross multiply
    1,287.80x = 1,931.88 × 422
  4. Step 4: Simplify right side
    1,287.80x = 815,253.36
  5. Step 5: Solve for x
    x = 815,253.36/1,287.80
  6. Step 6: Final answer
    x = 633.06

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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.