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Finding the Fourth Proportional to 840.80, 1,261.20 and 747.20

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Solution

The fourth proportional to 840.80, 1,261.20 and 747.20 is: 1,120.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    840.80 : 1,261.20 = 747.20 : x
  2. Step 2: Convert to fraction form
    840.80/1,261.20 = 747.20/x
  3. Step 3: Cross multiply
    840.80x = 1,261.20 × 747.20
  4. Step 4: Simplify right side
    840.80x = 942,368.64
  5. Step 5: Solve for x
    x = 942,368.64/840.80
  6. Step 6: Final answer
    x = 1,120.80

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.