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Finding the Fourth Proportional to 991.58, 1,368.54 and 643.28

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Solution

The fourth proportional to 991.58, 1,368.54 and 643.28 is: 887.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.58 : 1,368.54 = 643.28 : x
  2. Step 2: Convert to fraction form
    991.58/1,368.54 = 643.28/x
  3. Step 3: Cross multiply
    991.58x = 1,368.54 × 643.28
  4. Step 4: Simplify right side
    991.58x = 880,354.41
  5. Step 5: Solve for x
    x = 880,354.41/991.58
  6. Step 6: Final answer
    x = 887.83

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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.