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The number 1621 was subtracted from 6244 in base x. If the result was 4323,...

Mathematics
WAEC 2024

The number 1621 was subtracted from 6244 in base x. If the result was 4323, find x.

  • A. Seven
  • B. Eight
  • C. Nine
  • D. Ten
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Correct Answer: Option A
Explanation

 Given that \( 6244_x - 1621_x = 4323_x \), find the value of \( x \).

{Step 1: Convert to decimal:}
\[6244_x = 6x^3 + 2x^2 + 4x + 4\]
\[1621_x = 1x^3 + 6x^2 + 2x + 1\]
\[4323_x = 4x^3 + 3x^2 + 2x + 3\]

f{Step 2: Set up the equation:}
\[(6x^3 + 2x^2 + 4x + 4) - (1x^3 + 6x^2 + 2x + 1) = 4x^3 + 3x^2 + 2x + 3\]

{Step 3: Simplify the left side:}
\[(6x^3 - 1x^3) + (2x^2 - 6x^2) + (4x - 2x) + (4 - 1) = 5x^3 - 4x^2 + 2x + 3\]

{Step 4: Set the equation:}
\[5x^3 - 4x^2 + 2x + 3 = 4x^3 + 3x^2 + 2x + 3\]

{Step 5: Combine like terms:}
\[5x^3 - 4x^3 - 4x^2 - 3x^2 + 2x - 2x + 3 - 3 = 0\]
\[x^3 - 7x^2 = 0\]

{Step 6: Factor the equation:}
\[x^2(x - 7) = 0\]

{Step 7: Solutions:}
\[x = 7 \quad (\text{valid}), \quad x = 0 \quad (\text{not valid})\]

\Thus, the base \( x \) is 7


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