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Finding the Fourth Proportional to 838.92, 1,258.68 and 428.40

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Solution

The fourth proportional to 838.92, 1,258.68 and 428.40 is: 642.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    838.92 : 1,258.68 = 428.40 : x
  2. Step 2: Convert to fraction form
    838.92/1,258.68 = 428.40/x
  3. Step 3: Cross multiply
    838.92x = 1,258.68 × 428.40
  4. Step 4: Simplify right side
    838.92x = 539,218.51
  5. Step 5: Solve for x
    x = 539,218.51/838.92
  6. Step 6: Final answer
    x = 642.75

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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.