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Finding the Fourth Proportional to 686.40, 947.16 and 391.68

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Solution

The fourth proportional to 686.40, 947.16 and 391.68 is: 540.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.40 : 947.16 = 391.68 : x
  2. Step 2: Convert to fraction form
    686.40/947.16 = 391.68/x
  3. Step 3: Cross multiply
    686.40x = 947.16 × 391.68
  4. Step 4: Simplify right side
    686.40x = 370,983.63
  5. Step 5: Solve for x
    x = 370,983.63/686.40
  6. Step 6: Final answer
    x = 540.48

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1.5x scale

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.