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Finding the Fourth Proportional to 1,421, 2,129.64 and 640.96

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Solution

The fourth proportional to 1,421, 2,129.64 and 640.96 is: 960.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,421 : 2,129.64 = 640.96 : x
  2. Step 2: Convert to fraction form
    1,421/2,129.64 = 640.96/x
  3. Step 3: Cross multiply
    1,421x = 2,129.64 × 640.96
  4. Step 4: Simplify right side
    1,421x = 1,365,014.05
  5. Step 5: Solve for x
    x = 1,365,014.05/1,421
  6. Step 6: Final answer
    x = 960.60

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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.