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Finding the Fourth Proportional to 1,287.64, 1,931.05 and 421.75

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Solution

The fourth proportional to 1,287.64, 1,931.05 and 421.75 is: 632.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.64 : 1,931.05 = 421.75 : x
  2. Step 2: Convert to fraction form
    1,287.64/1,931.05 = 421.75/x
  3. Step 3: Cross multiply
    1,287.64x = 1,931.05 × 421.75
  4. Step 4: Simplify right side
    1,287.64x = 814,420.34
  5. Step 5: Solve for x
    x = 814,420.34/1,287.64
  6. Step 6: Final answer
    x = 632.49

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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.