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Finding the Fourth Proportional to 921.06, 1,271.16 and 687.78

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Solution

The fourth proportional to 921.06, 1,271.16 and 687.78 is: 949.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    921.06 : 1,271.16 = 687.78 : x
  2. Step 2: Convert to fraction form
    921.06/1,271.16 = 687.78/x
  3. Step 3: Cross multiply
    921.06x = 1,271.16 × 687.78
  4. Step 4: Simplify right side
    921.06x = 874,278.42
  5. Step 5: Solve for x
    x = 874,278.42/921.06
  6. Step 6: Final answer
    x = 949.21

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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.