How many tapes would Turing Machine require to find the sum of 2 integers (expressed in base2)?
Anything that can be computed with any reasonable extension of a Turing machine can be computed with the standard Turing machine that has a single one-way infinite tape.

For example, you can simulate a four-tape machine by interleaving the characters of the tapes so that, e.g., the four tapes

$$\begin{array}{cccc}
    a_1 &amp; a_2 &amp; a_3 &amp; \cdots\\
    b_1 &amp; b_2 &amp; b_3 &amp; \cdots\\
    c_1 &amp; c_2 &amp; c_3 &amp; \cdots\\
    d_1 &amp; d_2 &amp; d_3 &amp; \cdots
\end{array}$$

with the single tape
$$a_1\ b_1\ c_1\ d_1\ a_2\ b_2\ c_2\ d_2\ a_3\ b_3\ c_3\ d_3\ \cdots$$