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Finding the Fourth Proportional to 991.59, 1,485.25 and 643.90

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Solution

The fourth proportional to 991.59, 1,485.25 and 643.90 is: 964.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.59 : 1,485.25 = 643.90 : x
  2. Step 2: Convert to fraction form
    991.59/1,485.25 = 643.90/x
  3. Step 3: Cross multiply
    991.59x = 1,485.25 × 643.90
  4. Step 4: Simplify right side
    991.59x = 956,352.48
  5. Step 5: Solve for x
    x = 956,352.48/991.59
  6. Step 6: Final answer
    x = 964.46

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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.