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Finding the Fourth Proportional to 785.70, 1,178.78 and 420.21

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Solution

The fourth proportional to 785.70, 1,178.78 and 420.21 is: 630.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    785.70 : 1,178.78 = 420.21 : x
  2. Step 2: Convert to fraction form
    785.70/1,178.78 = 420.21/x
  3. Step 3: Cross multiply
    785.70x = 1,178.78 × 420.21
  4. Step 4: Simplify right side
    785.70x = 495,333.04
  5. Step 5: Solve for x
    x = 495,333.04/785.70
  6. Step 6: Final answer
    x = 630.44

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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.