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Finding the Fourth Proportional to 1,390.21, 1,915.24 and 969.80

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Solution

The fourth proportional to 1,390.21, 1,915.24 and 969.80 is: 1,336.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.21 : 1,915.24 = 969.80 : x
  2. Step 2: Convert to fraction form
    1,390.21/1,915.24 = 969.80/x
  3. Step 3: Cross multiply
    1,390.21x = 1,915.24 × 969.80
  4. Step 4: Simplify right side
    1,390.21x = 1,857,394.90
  5. Step 5: Solve for x
    x = 1,857,394.90/1,390.21
  6. Step 6: Final answer
    x = 1,336.05

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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.