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Finding the Third Proportional to 780 and 1,220

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Solution

The third proportional to 780 and 1,220 is: 1,908.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    780 : 1,220 = 1,220 : x
  2. Step 2: Convert to fraction form
    780/1,220 = 1,220/x
  3. Step 3: Cross multiply
    780x = 1,220 × 1,220
  4. Step 4: Simplify right side
    780x = 1,488,400
  5. Step 5: Solve for x
    x = 1,488,400/780
  6. Step 6: Final answer
    x = 1,908.21

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Why These Related Problems?

These problems maintain the same ratio (1.56) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.