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Finding the Fourth Proportional to 776.80, 1,071.12 and 643.60

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Solution

The fourth proportional to 776.80, 1,071.12 and 643.60 is: 887.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    776.80 : 1,071.12 = 643.60 : x
  2. Step 2: Convert to fraction form
    776.80/1,071.12 = 643.60/x
  3. Step 3: Cross multiply
    776.80x = 1,071.12 × 643.60
  4. Step 4: Simplify right side
    776.80x = 689,372.83
  5. Step 5: Solve for x
    x = 689,372.83/776.80
  6. Step 6: Final answer
    x = 887.45

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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.