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Finding the Fourth Proportional to 979.61, 1,350.98 and 643.21

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Solution

The fourth proportional to 979.61, 1,350.98 and 643.21 is: 887.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    979.61 : 1,350.98 = 643.21 : x
  2. Step 2: Convert to fraction form
    979.61/1,350.98 = 643.21/x
  3. Step 3: Cross multiply
    979.61x = 1,350.98 × 643.21
  4. Step 4: Simplify right side
    979.61x = 868,959.66
  5. Step 5: Solve for x
    x = 868,959.66/979.61
  6. Step 6: Final answer
    x = 887.05

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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.