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Finding the Fourth Proportional to 987.20, 1,480.80 and 915.20

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Solution

The fourth proportional to 987.20, 1,480.80 and 915.20 is: 1,372.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.20 : 1,480.80 = 915.20 : x
  2. Step 2: Convert to fraction form
    987.20/1,480.80 = 915.20/x
  3. Step 3: Cross multiply
    987.20x = 1,480.80 × 915.20
  4. Step 4: Simplify right side
    987.20x = 1,355,228.16
  5. Step 5: Solve for x
    x = 1,355,228.16/987.20
  6. Step 6: Final answer
    x = 1,372.80

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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.