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Finding the Fourth Proportional to 987.18, 1,478.74 and 553.42

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Solution

The fourth proportional to 987.18, 1,478.74 and 553.42 is: 828.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.18 : 1,478.74 = 553.42 : x
  2. Step 2: Convert to fraction form
    987.18/1,478.74 = 553.42/x
  3. Step 3: Cross multiply
    987.18x = 1,478.74 × 553.42
  4. Step 4: Simplify right side
    987.18x = 818,364.29
  5. Step 5: Solve for x
    x = 818,364.29/987.18
  6. Step 6: Final answer
    x = 828.99

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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.