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Finding the Fourth Proportional to 690.21, 1,035.54 and 639.63

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Solution

The fourth proportional to 690.21, 1,035.54 and 639.63 is: 959.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    690.21 : 1,035.54 = 639.63 : x
  2. Step 2: Convert to fraction form
    690.21/1,035.54 = 639.63/x
  3. Step 3: Cross multiply
    690.21x = 1,035.54 × 639.63
  4. Step 4: Simplify right side
    690.21x = 662,362.45
  5. Step 5: Solve for x
    x = 662,362.45/690.21
  6. Step 6: Final answer
    x = 959.65

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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.