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Finding the Fourth Proportional to 1,387.90, 1,915.14 and 828.40

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Solution

The fourth proportional to 1,387.90, 1,915.14 and 828.40 is: 1,143.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,387.90 : 1,915.14 = 828.40 : x
  2. Step 2: Convert to fraction form
    1,387.90/1,915.14 = 828.40/x
  3. Step 3: Cross multiply
    1,387.90x = 1,915.14 × 828.40
  4. Step 4: Simplify right side
    1,387.90x = 1,586,501.98
  5. Step 5: Solve for x
    x = 1,586,501.98/1,387.90
  6. Step 6: Final answer
    x = 1,143.10

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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.