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Finding the Fourth Proportional to 987.12, 1,362.35 and 821.05

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Solution

The fourth proportional to 987.12, 1,362.35 and 821.05 is: 1,133.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.12 : 1,362.35 = 821.05 : x
  2. Step 2: Convert to fraction form
    987.12/1,362.35 = 821.05/x
  3. Step 3: Cross multiply
    987.12x = 1,362.35 × 821.05
  4. Step 4: Simplify right side
    987.12x = 1,118,556.11
  5. Step 5: Solve for x
    x = 1,118,556.11/987.12
  6. Step 6: Final answer
    x = 1,133.15

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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.