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Finding the Fourth Proportional to 786.50, 1,179.85 and 420.78

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Solution

The fourth proportional to 786.50, 1,179.85 and 420.78 is: 631.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    786.50 : 1,179.85 = 420.78 : x
  2. Step 2: Convert to fraction form
    786.50/1,179.85 = 420.78/x
  3. Step 3: Cross multiply
    786.50x = 1,179.85 × 420.78
  4. Step 4: Simplify right side
    786.50x = 496,457.28
  5. Step 5: Solve for x
    x = 496,457.28/786.50
  6. Step 6: Final answer
    x = 631.22

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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.