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Finding the Fourth Proportional to 921.42, 1,272 and 642.60

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Solution

The fourth proportional to 921.42, 1,272 and 642.60 is: 887.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    921.42 : 1,272 = 642.60 : x
  2. Step 2: Convert to fraction form
    921.42/1,272 = 642.60/x
  3. Step 3: Cross multiply
    921.42x = 1,272 × 642.60
  4. Step 4: Simplify right side
    921.42x = 817,387.20
  5. Step 5: Solve for x
    x = 817,387.20/921.42
  6. Step 6: Final answer
    x = 887.10

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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.