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Finding the Fourth Proportional to 686.40, 1,024.56 and 643.20

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Solution

The fourth proportional to 686.40, 1,024.56 and 643.20 is: 960.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.40 : 1,024.56 = 643.20 : x
  2. Step 2: Convert to fraction form
    686.40/1,024.56 = 643.20/x
  3. Step 3: Cross multiply
    686.40x = 1,024.56 × 643.20
  4. Step 4: Simplify right side
    686.40x = 658,996.99
  5. Step 5: Solve for x
    x = 658,996.99/686.40
  6. Step 6: Final answer
    x = 960.08

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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.