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Finding the Fourth Proportional to 861.40, 1,290.30 and 644.68

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Solution

The fourth proportional to 861.40, 1,290.30 and 644.68 is: 965.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.40 : 1,290.30 = 644.68 : x
  2. Step 2: Convert to fraction form
    861.40/1,290.30 = 644.68/x
  3. Step 3: Cross multiply
    861.40x = 1,290.30 × 644.68
  4. Step 4: Simplify right side
    861.40x = 831,830.60
  5. Step 5: Solve for x
    x = 831,830.60/861.40
  6. Step 6: Final answer
    x = 965.67

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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.