16Hit1600
AlgebraVery hardConstants for a dependent system

Algebra practice question

The system ax + 3y = 12 and 4x + 6y = k, where a and k are constants, has infinitely many solutions. What is the value of a + k?

Answer: 26

The second equation must be a multiple of the first: 6 = 2 × 3, so a = 4/2 = 2 and k = 2 × 12 = 24. Then a + k = 26.

Common wrong answers

If you answered 2
2 is a alone.
If you answered 14
14 uses a = 2 with k = 12, forgetting to double the constant.
If you answered 28
28 uses a = 4 instead of 2.

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