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Finding the Fourth Proportional to 875.72, 1,208.34 and 643.40

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Solution

The fourth proportional to 875.72, 1,208.34 and 643.40 is: 887.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    875.72 : 1,208.34 = 643.40 : x
  2. Step 2: Convert to fraction form
    875.72/1,208.34 = 643.40/x
  3. Step 3: Cross multiply
    875.72x = 1,208.34 × 643.40
  4. Step 4: Simplify right side
    875.72x = 777,445.96
  5. Step 5: Solve for x
    x = 777,445.96/875.72
  6. Step 6: Final answer
    x = 887.78

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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.