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Finding the Fourth Proportional to 947.70, 1,421.94 and 639.60

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Solution

The fourth proportional to 947.70, 1,421.94 and 639.60 is: 959.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    947.70 : 1,421.94 = 639.60 : x
  2. Step 2: Convert to fraction form
    947.70/1,421.94 = 639.60/x
  3. Step 3: Cross multiply
    947.70x = 1,421.94 × 639.60
  4. Step 4: Simplify right side
    947.70x = 909,472.82
  5. Step 5: Solve for x
    x = 909,472.82/947.70
  6. Step 6: Final answer
    x = 959.66

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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.