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Finding the Fourth Proportional to 991.78, 1,369.26 and 660.70

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Solution

The fourth proportional to 991.78, 1,369.26 and 660.70 is: 912.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.78 : 1,369.26 = 660.70 : x
  2. Step 2: Convert to fraction form
    991.78/1,369.26 = 660.70/x
  3. Step 3: Cross multiply
    991.78x = 1,369.26 × 660.70
  4. Step 4: Simplify right side
    991.78x = 904,670.08
  5. Step 5: Solve for x
    x = 904,670.08/991.78
  6. Step 6: Final answer
    x = 912.17

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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.