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Finding the Fourth Proportional to 1,206.78, 1,665.38 and 787.40

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Solution

The fourth proportional to 1,206.78, 1,665.38 and 787.40 is: 1,086.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,206.78 : 1,665.38 = 787.40 : x
  2. Step 2: Convert to fraction form
    1,206.78/1,665.38 = 787.40/x
  3. Step 3: Cross multiply
    1,206.78x = 1,665.38 × 787.40
  4. Step 4: Simplify right side
    1,206.78x = 1,311,320.21
  5. Step 5: Solve for x
    x = 1,311,320.21/1,206.78
  6. Step 6: Final answer
    x = 1,086.63

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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.