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Finding the Fourth Proportional to 1,320.78, 1,979.34 and 772.20

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Solution

The fourth proportional to 1,320.78, 1,979.34 and 772.20 is: 1,157.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,320.78 : 1,979.34 = 772.20 : x
  2. Step 2: Convert to fraction form
    1,320.78/1,979.34 = 772.20/x
  3. Step 3: Cross multiply
    1,320.78x = 1,979.34 × 772.20
  4. Step 4: Simplify right side
    1,320.78x = 1,528,451.30
  5. Step 5: Solve for x
    x = 1,528,451.30/1,320.78
  6. Step 6: Final answer
    x = 1,157.24

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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.