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Finding the Fourth Proportional to 1,242.50, 1,859.78 and 780.80

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Solution

The fourth proportional to 1,242.50, 1,859.78 and 780.80 is: 1,168.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,242.50 : 1,859.78 = 780.80 : x
  2. Step 2: Convert to fraction form
    1,242.50/1,859.78 = 780.80/x
  3. Step 3: Cross multiply
    1,242.50x = 1,859.78 × 780.80
  4. Step 4: Simplify right side
    1,242.50x = 1,452,108.88
  5. Step 5: Solve for x
    x = 1,452,108.88/1,242.50
  6. Step 6: Final answer
    x = 1,168.70

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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.