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Finding the Fourth Proportional to 1,393.20, 1,921.78 and 921.12

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Solution

The fourth proportional to 1,393.20, 1,921.78 and 921.12 is: 1,270.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,393.20 : 1,921.78 = 921.12 : x
  2. Step 2: Convert to fraction form
    1,393.20/1,921.78 = 921.12/x
  3. Step 3: Cross multiply
    1,393.20x = 1,921.78 × 921.12
  4. Step 4: Simplify right side
    1,393.20x = 1,770,189.99
  5. Step 5: Solve for x
    x = 1,770,189.99/1,393.20
  6. Step 6: Final answer
    x = 1,270.59

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1.5x scale

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.