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Finding the Fourth Proportional to 921.84, 1,271.88 and 641.76

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Solution

The fourth proportional to 921.84, 1,271.88 and 641.76 is: 885.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    921.84 : 1,271.88 = 641.76 : x
  2. Step 2: Convert to fraction form
    921.84/1,271.88 = 641.76/x
  3. Step 3: Cross multiply
    921.84x = 1,271.88 × 641.76
  4. Step 4: Simplify right side
    921.84x = 816,241.71
  5. Step 5: Solve for x
    x = 816,241.71/921.84
  6. Step 6: Final answer
    x = 885.45

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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.