3. Among the 35 numbers $1^{2}, 2^{2}, 3^{2}, \cdots, 35^{2}$, the numbers with an odd digit in the tens place are $\qquad$ in total.
3. 7. Among $1^{2}, 2^{2}, \cdots, 9^{2}$, those with an odd tens digit are only $4^{2}=16, 6^{2}=36$.
The square of a two-digit number can be expressed as
$$
(10 a+b)^{2}=100 a^{2}+20 a b+b^{2} \text {. }
$$

It is evident that, when the unit digit is $A$ and $\hat{C}$, the tens digit of the square is odd. That is, only $4^{2}, 6^{2}, 14^{2}, 16^{2}, 24^{2}, 26^{2}, 34^{2}$ have