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Finding the Fourth Proportional to 991.56, 1,368.36 and 642.25

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Solution

The fourth proportional to 991.56, 1,368.36 and 642.25 is: 886.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.56 : 1,368.36 = 642.25 : x
  2. Step 2: Convert to fraction form
    991.56/1,368.36 = 642.25/x
  3. Step 3: Cross multiply
    991.56x = 1,368.36 × 642.25
  4. Step 4: Simplify right side
    991.56x = 878,829.21
  5. Step 5: Solve for x
    x = 878,829.21/991.56
  6. Step 6: Final answer
    x = 886.31

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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.