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Finding the Fourth Proportional to 915.20, 1,372.80 and 787.20

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Solution

The fourth proportional to 915.20, 1,372.80 and 787.20 is: 1,180.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    915.20 : 1,372.80 = 787.20 : x
  2. Step 2: Convert to fraction form
    915.20/1,372.80 = 787.20/x
  3. Step 3: Cross multiply
    915.20x = 1,372.80 × 787.20
  4. Step 4: Simplify right side
    915.20x = 1,080,668.16
  5. Step 5: Solve for x
    x = 1,080,668.16/915.20
  6. Step 6: Final answer
    x = 1,180.80

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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.