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Finding the Fourth Proportional to 678.40, 1,016.70 and 485.80

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Solution

The fourth proportional to 678.40, 1,016.70 and 485.80 is: 728.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.40 : 1,016.70 = 485.80 : x
  2. Step 2: Convert to fraction form
    678.40/1,016.70 = 485.80/x
  3. Step 3: Cross multiply
    678.40x = 1,016.70 × 485.80
  4. Step 4: Simplify right side
    678.40x = 493,912.86
  5. Step 5: Solve for x
    x = 493,912.86/678.40
  6. Step 6: Final answer
    x = 728.06

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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.