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Finding the Fourth Proportional to 991.04, 1,367.70 and 978.80

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Solution

The fourth proportional to 991.04, 1,367.70 and 978.80 is: 1,350.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.04 : 1,367.70 = 978.80 : x
  2. Step 2: Convert to fraction form
    991.04/1,367.70 = 978.80/x
  3. Step 3: Cross multiply
    991.04x = 1,367.70 × 978.80
  4. Step 4: Simplify right side
    991.04x = 1,338,704.76
  5. Step 5: Solve for x
    x = 1,338,704.76/991.04
  6. Step 6: Final answer
    x = 1,350.81

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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.