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Finding the Fourth Proportional to 1,369.72, 2,055.80 and 639.70

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Solution

The fourth proportional to 1,369.72, 2,055.80 and 639.70 is: 960.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,369.72 : 2,055.80 = 639.70 : x
  2. Step 2: Convert to fraction form
    1,369.72/2,055.80 = 639.70/x
  3. Step 3: Cross multiply
    1,369.72x = 2,055.80 × 639.70
  4. Step 4: Simplify right side
    1,369.72x = 1,315,095.26
  5. Step 5: Solve for x
    x = 1,315,095.26/1,369.72
  6. Step 6: Final answer
    x = 960.12

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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.