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Finding the Fourth Proportional to 939.40, 1,409.10 and 647.80

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Solution

The fourth proportional to 939.40, 1,409.10 and 647.80 is: 971.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    939.40 : 1,409.10 = 647.80 : x
  2. Step 2: Convert to fraction form
    939.40/1,409.10 = 647.80/x
  3. Step 3: Cross multiply
    939.40x = 1,409.10 × 647.80
  4. Step 4: Simplify right side
    939.40x = 912,814.98
  5. Step 5: Solve for x
    x = 912,814.98/939.40
  6. Step 6: Final answer
    x = 971.70

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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.