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Finding the Fourth Proportional to 931.80, 1,397.70 and 640.20

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Solution

The fourth proportional to 931.80, 1,397.70 and 640.20 is: 960.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    931.80 : 1,397.70 = 640.20 : x
  2. Step 2: Convert to fraction form
    931.80/1,397.70 = 640.20/x
  3. Step 3: Cross multiply
    931.80x = 1,397.70 × 640.20
  4. Step 4: Simplify right side
    931.80x = 894,807.54
  5. Step 5: Solve for x
    x = 894,807.54/931.80
  6. Step 6: Final answer
    x = 960.30

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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.