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Finding the Fourth Proportional to 917.76, 1,267.20 and 641.28

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Solution

The fourth proportional to 917.76, 1,267.20 and 641.28 is: 885.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    917.76 : 1,267.20 = 641.28 : x
  2. Step 2: Convert to fraction form
    917.76/1,267.20 = 641.28/x
  3. Step 3: Cross multiply
    917.76x = 1,267.20 × 641.28
  4. Step 4: Simplify right side
    917.76x = 812,630.02
  5. Step 5: Solve for x
    x = 812,630.02/917.76
  6. Step 6: Final answer
    x = 885.45

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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.