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Finding the Fourth Proportional to 990.74, 1,368.21 and 641.63

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Solution

The fourth proportional to 990.74, 1,368.21 and 641.63 is: 886.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.74 : 1,368.21 = 641.63 : x
  2. Step 2: Convert to fraction form
    990.74/1,368.21 = 641.63/x
  3. Step 3: Cross multiply
    990.74x = 1,368.21 × 641.63
  4. Step 4: Simplify right side
    990.74x = 877,877.74
  5. Step 5: Solve for x
    x = 877,877.74/990.74
  6. Step 6: Final answer
    x = 886.09

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.