waecmaths question:
If 7 + y = 4(mod 8). Find the least value if $10\le y\le 30$
Option A:
11
Option B:
13
Option C:
19
Option D:
21
waecmaths solution:
$\begin{align} & 7+y=4(\bmod 8) \\ & \text{Testing from the range given } \\ & 7+10=1(\bmod 8) \\ & 7+11=2(mod8) \\ & 7+12=3(\bmod 8) \\ & 7+13=4(mod8) \\ & \text{The least value of }y\text{ is }13 \\\end{align}$
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