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Finding the Fourth Proportional to 742.40, 1,112.40 and 639.20

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Solution

The fourth proportional to 742.40, 1,112.40 and 639.20 is: 957.77

Step by Step Solution

  1. Step 1: Write the proportion equation
    742.40 : 1,112.40 = 639.20 : x
  2. Step 2: Convert to fraction form
    742.40/1,112.40 = 639.20/x
  3. Step 3: Cross multiply
    742.40x = 1,112.40 × 639.20
  4. Step 4: Simplify right side
    742.40x = 711,046.08
  5. Step 5: Solve for x
    x = 711,046.08/742.40
  6. Step 6: Final answer
    x = 957.77

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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.