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Finding the Fourth Proportional to 1,288.80, 1,934.64 and 639.36

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Solution

The fourth proportional to 1,288.80, 1,934.64 and 639.36 is: 959.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,288.80 : 1,934.64 = 639.36 : x
  2. Step 2: Convert to fraction form
    1,288.80/1,934.64 = 639.36/x
  3. Step 3: Cross multiply
    1,288.80x = 1,934.64 × 639.36
  4. Step 4: Simplify right side
    1,288.80x = 1,236,931.43
  5. Step 5: Solve for x
    x = 1,236,931.43/1,288.80
  6. Step 6: Final answer
    x = 959.75

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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.