Simplify the following, leaving your answer in standard form.

$(0.2\times {10}^{17})\times (0.7\times {10}^{16})$

Simplify the following, leaving your answer in standard form.

$(9\times {10}^{17})÷(3\times {10}^{16})$

Simplify the following, leaving your answer in standard form.

$(8\times {10}^{17})÷(4\times {10}^{16})$

Simplify the following, leaving your answer in standard form.

$(1.5\times {10}^8)÷(5\times {10}^4)$

Simplify the following, leaving your answer in standard form.

$(2.4\times {10}^{64})÷(8\times {10}^{21})$

Simplify the following, leaving your answer in standard form.

$(1.44\times {10}^7)÷(1.2\times {10}^4)$

Simplify the following, leaving your answer in standard form.

$\frac{(1.7\times {10}^8)}{(3.4\times {10}^5)}$

Simplify the following, leaving your answer in standard form.

$(4.9\times {10}^5)\times (3.6\times {10}^9)$

Simplify the following, leaving your answer in standard form.

$(3\times {10}^4)+(4\times {10}^3)$