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Finding the Fourth Proportional to 1,287.47, 1,931.22 and 421.79

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Solution

The fourth proportional to 1,287.47, 1,931.22 and 421.79 is: 632.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.47 : 1,931.22 = 421.79 : x
  2. Step 2: Convert to fraction form
    1,287.47/1,931.22 = 421.79/x
  3. Step 3: Cross multiply
    1,287.47x = 1,931.22 × 421.79
  4. Step 4: Simplify right side
    1,287.47x = 814,559.63
  5. Step 5: Solve for x
    x = 814,559.63/1,287.47
  6. Step 6: Final answer
    x = 632.68

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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.