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Finding the Fourth Proportional to 855.12, 1,290 and 821.10

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Solution

The fourth proportional to 855.12, 1,290 and 821.10 is: 1,238.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    855.12 : 1,290 = 821.10 : x
  2. Step 2: Convert to fraction form
    855.12/1,290 = 821.10/x
  3. Step 3: Cross multiply
    855.12x = 1,290 × 821.10
  4. Step 4: Simplify right side
    855.12x = 1,059,219
  5. Step 5: Solve for x
    x = 1,059,219/855.12
  6. Step 6: Final answer
    x = 1,238.68

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.