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Finding the Fourth Proportional to 990.21, 1,485.36 and 259.86

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Solution

The fourth proportional to 990.21, 1,485.36 and 259.86 is: 389.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.21 : 1,485.36 = 259.86 : x
  2. Step 2: Convert to fraction form
    990.21/1,485.36 = 259.86/x
  3. Step 3: Cross multiply
    990.21x = 1,485.36 × 259.86
  4. Step 4: Simplify right side
    990.21x = 385,985.65
  5. Step 5: Solve for x
    x = 385,985.65/990.21
  6. Step 6: Final answer
    x = 389.80

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1.5x scale

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.