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Finding the Fourth Proportional to 1,222.51, 1,687.61 and 781

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Solution

The fourth proportional to 1,222.51, 1,687.61 and 781 is: 1,078.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,222.51 : 1,687.61 = 781 : x
  2. Step 2: Convert to fraction form
    1,222.51/1,687.61 = 781/x
  3. Step 3: Cross multiply
    1,222.51x = 1,687.61 × 781
  4. Step 4: Simplify right side
    1,222.51x = 1,318,023.41
  5. Step 5: Solve for x
    x = 1,318,023.41/1,222.51
  6. Step 6: Final answer
    x = 1,078.13

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.