Question
How many two-digit numbers are duvisible by $3$?
✓
Answer
The two-digit numbers divisible by $3$ start from
$12, 15, 18, 21, ..., 99$
Here,
$a = 12$
$d = 3$
$a_n = a + (n - 1)d$
$\Rightarrow 99 = 12 + (n - 1)(3)$
$\Rightarrow 99 = 12 + 3n - 3$
$\Rightarrow 90 = 3n$
$\Rightarrow n = 30$
This, $30$ two-digit number are divisible by $3$.
$12, 15, 18, 21, ..., 99$
Here,
$a = 12$
$d = 3$
$a_n = a + (n - 1)d$
$\Rightarrow 99 = 12 + (n - 1)(3)$
$\Rightarrow 99 = 12 + 3n - 3$
$\Rightarrow 90 = 3n$
$\Rightarrow n = 30$
This, $30$ two-digit number are divisible by $3$.
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