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Finding the Fourth Proportional to 876.72, 1,209.72 and 644.40

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Solution

The fourth proportional to 876.72, 1,209.72 and 644.40 is: 889.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    876.72 : 1,209.72 = 644.40 : x
  2. Step 2: Convert to fraction form
    876.72/1,209.72 = 644.40/x
  3. Step 3: Cross multiply
    876.72x = 1,209.72 × 644.40
  4. Step 4: Simplify right side
    876.72x = 779,543.57
  5. Step 5: Solve for x
    x = 779,543.57/876.72
  6. Step 6: Final answer
    x = 889.16

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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.