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Finding the Fourth Proportional to 678.10, 1,015.80 and 389.20

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Solution

The fourth proportional to 678.10, 1,015.80 and 389.20 is: 583.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.10 : 1,015.80 = 389.20 : x
  2. Step 2: Convert to fraction form
    678.10/1,015.80 = 389.20/x
  3. Step 3: Cross multiply
    678.10x = 1,015.80 × 389.20
  4. Step 4: Simplify right side
    678.10x = 395,349.36
  5. Step 5: Solve for x
    x = 395,349.36/678.10
  6. Step 6: Final answer
    x = 583.03

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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.