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Finding the Fourth Proportional to 1,391.64, 2,087.28 and 661.68

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Solution

The fourth proportional to 1,391.64, 2,087.28 and 661.68 is: 992.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,391.64 : 2,087.28 = 661.68 : x
  2. Step 2: Convert to fraction form
    1,391.64/2,087.28 = 661.68/x
  3. Step 3: Cross multiply
    1,391.64x = 2,087.28 × 661.68
  4. Step 4: Simplify right side
    1,391.64x = 1,381,111.43
  5. Step 5: Solve for x
    x = 1,381,111.43/1,391.64
  6. Step 6: Final answer
    x = 992.43

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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.