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WAEC Mathematics 2016 Paper

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Question : 38

Total: 49

If 20(mod 9) is equivalent to y(mod 6), find y.

1
2
3
4

Solution:

Concept:

Reduce

20 \pmod{9}

first, then compare the result with

y \pmod{6}

.

Explanation:

Compute

20 \pmod{9}

.

Divide

20

by

9

:

9 \times 2 = 18

, leaving remainder

2

.

So

20 \equiv 2 \pmod{9}

.

Now the problem states this is equivalent to

y \pmod{6}

.

Thus

y

must match the same remainder value, which is

2

.

Checking:

2 \pmod{6}

also gives remainder

2

.

This value is present in option B.

Answer:

y = 2

Correct option: B.

2

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