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Finding the Fourth Proportional to 1,387.16, 1,913.91 and 921.41

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Solution

The fourth proportional to 1,387.16, 1,913.91 and 921.41 is: 1,271.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,387.16 : 1,913.91 = 921.41 : x
  2. Step 2: Convert to fraction form
    1,387.16/1,913.91 = 921.41/x
  3. Step 3: Cross multiply
    1,387.16x = 1,913.91 × 921.41
  4. Step 4: Simplify right side
    1,387.16x = 1,763,486.24
  5. Step 5: Solve for x
    x = 1,763,486.24/1,387.16
  6. Step 6: Final answer
    x = 1,271.30

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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.