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Finding the Fourth Proportional to 1,280, 1,920.64 and 672

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Solution

The fourth proportional to 1,280, 1,920.64 and 672 is: 1,008.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,280 : 1,920.64 = 672 : x
  2. Step 2: Convert to fraction form
    1,280/1,920.64 = 672/x
  3. Step 3: Cross multiply
    1,280x = 1,920.64 × 672
  4. Step 4: Simplify right side
    1,280x = 1,290,670.08
  5. Step 5: Solve for x
    x = 1,290,670.08/1,280
  6. Step 6: Final answer
    x = 1,008.34

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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.