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Finding the Fourth Proportional to 1,215, 1,678.14 and 821.34

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Solution

The fourth proportional to 1,215, 1,678.14 and 821.34 is: 1,134.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,215 : 1,678.14 = 821.34 : x
  2. Step 2: Convert to fraction form
    1,215/1,678.14 = 821.34/x
  3. Step 3: Cross multiply
    1,215x = 1,678.14 × 821.34
  4. Step 4: Simplify right side
    1,215x = 1,378,323.51
  5. Step 5: Solve for x
    x = 1,378,323.51/1,215
  6. Step 6: Final answer
    x = 1,134.42

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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.