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Finding the Fourth Proportional to 991.56, 1,368.17 and 642.05

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Solution

The fourth proportional to 991.56, 1,368.17 and 642.05 is: 885.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.56 : 1,368.17 = 642.05 : x
  2. Step 2: Convert to fraction form
    991.56/1,368.17 = 642.05/x
  3. Step 3: Cross multiply
    991.56x = 1,368.17 × 642.05
  4. Step 4: Simplify right side
    991.56x = 878,428.31
  5. Step 5: Solve for x
    x = 878,428.31/991.56
  6. Step 6: Final answer
    x = 885.91

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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.