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Finding the Fourth Proportional to 991.80, 1,368.36 and 642.69

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Solution

The fourth proportional to 991.80, 1,368.36 and 642.69 is: 886.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.80 : 1,368.36 = 642.69 : x
  2. Step 2: Convert to fraction form
    991.80/1,368.36 = 642.69/x
  3. Step 3: Cross multiply
    991.80x = 1,368.36 × 642.69
  4. Step 4: Simplify right side
    991.80x = 879,431.29
  5. Step 5: Solve for x
    x = 879,431.29/991.80
  6. Step 6: Final answer
    x = 886.70

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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.