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Finding the Fourth Proportional to 1,356.40, 2,031.40 and 921.20

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Solution

The fourth proportional to 1,356.40, 2,031.40 and 921.20 is: 1,379.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,356.40 : 2,031.40 = 921.20 : x
  2. Step 2: Convert to fraction form
    1,356.40/2,031.40 = 921.20/x
  3. Step 3: Cross multiply
    1,356.40x = 2,031.40 × 921.20
  4. Step 4: Simplify right side
    1,356.40x = 1,871,325.68
  5. Step 5: Solve for x
    x = 1,871,325.68/1,356.40
  6. Step 6: Final answer
    x = 1,379.63

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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.