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Finding the Fourth Proportional to 991.17, 1,368.63 and 642.47

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Solution

The fourth proportional to 991.17, 1,368.63 and 642.47 is: 887.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.17 : 1,368.63 = 642.47 : x
  2. Step 2: Convert to fraction form
    991.17/1,368.63 = 642.47/x
  3. Step 3: Cross multiply
    991.17x = 1,368.63 × 642.47
  4. Step 4: Simplify right side
    991.17x = 879,296.87
  5. Step 5: Solve for x
    x = 879,296.87/991.17
  6. Step 6: Final answer
    x = 887.13

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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.