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Finding the Fourth Proportional to 1,306.40, 1,959.78 and 428.60

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Solution

The fourth proportional to 1,306.40, 1,959.78 and 428.60 is: 642.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,306.40 : 1,959.78 = 428.60 : x
  2. Step 2: Convert to fraction form
    1,306.40/1,959.78 = 428.60/x
  3. Step 3: Cross multiply
    1,306.40x = 1,959.78 × 428.60
  4. Step 4: Simplify right side
    1,306.40x = 839,961.71
  5. Step 5: Solve for x
    x = 839,961.71/1,306.40
  6. Step 6: Final answer
    x = 642.96

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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.