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Finding the Fourth Proportional to 991.68, 1,369.68 and 678.36

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Solution

The fourth proportional to 991.68, 1,369.68 and 678.36 is: 936.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.68 : 1,369.68 = 678.36 : x
  2. Step 2: Convert to fraction form
    991.68/1,369.68 = 678.36/x
  3. Step 3: Cross multiply
    991.68x = 1,369.68 × 678.36
  4. Step 4: Simplify right side
    991.68x = 929,136.12
  5. Step 5: Solve for x
    x = 929,136.12/991.68
  6. Step 6: Final answer
    x = 936.93

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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.