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Finding the Fourth Proportional to 812.40, 1,215.90 and 715.20

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Solution

The fourth proportional to 812.40, 1,215.90 and 715.20 is: 1,070.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    812.40 : 1,215.90 = 715.20 : x
  2. Step 2: Convert to fraction form
    812.40/1,215.90 = 715.20/x
  3. Step 3: Cross multiply
    812.40x = 1,215.90 × 715.20
  4. Step 4: Simplify right side
    812.40x = 869,611.68
  5. Step 5: Solve for x
    x = 869,611.68/812.40
  6. Step 6: Final answer
    x = 1,070.42

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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.