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Finding the Fourth Proportional to 678.60, 1,017.90 and 638.10

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Solution

The fourth proportional to 678.60, 1,017.90 and 638.10 is: 957.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.60 : 1,017.90 = 638.10 : x
  2. Step 2: Convert to fraction form
    678.60/1,017.90 = 638.10/x
  3. Step 3: Cross multiply
    678.60x = 1,017.90 × 638.10
  4. Step 4: Simplify right side
    678.60x = 649,521.99
  5. Step 5: Solve for x
    x = 649,521.99/678.60
  6. Step 6: Final answer
    x = 957.15

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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.