The mass of the one atom of silver and lithium are $1.79\times {10}^{-25} \mathrm{kg}$ and $1.15\times {10}^{-26} \mathrm{kg}$ respectively. If the difference between their masses is $1.675\times {10}^{-k} \mathrm{kg}$, then the value of $k$ is

 The mass of the Sun is $1.99\times {10}^{30} \mathrm{kg}$ and the mass of the Mercury is $3.3\times {10}^{23}$ $\mathrm{kg}$. If the difference between the masses of the Sun and the mass of the Mercury is $\left(1.98999967\times {10}^a\right) \mathrm{kg}$, then $a$ is

If the thickness of a paper sheet of type $A$ is $0.0016 \mathrm{cm}$ and type $B$ is $0.0008 \mathrm{cm}$. Then find the sum of thicknesses of the paper sheet of each type. Which type of sheet is thicker?

If the size of the red blood cell is $0.000007 \mathrm{m}$ and the size of a plant cell is $0.00001275 \mathrm{m}$.Then, what is the difference between the sizes of the red blood cell and the plant cell?

Which one has a greater size?

The number of red blood cells per cubic millimeter of blood is approximately $5.5 \mathrm{million}$. If the average body contains $5 \mathrm{L}$ of blood, what is the total number of red cell in the body? Write in the standard form. $(1 \mathrm{L}=1000000 {\mathrm{mm}}^3)$

If the standard form of $243580000$ is $2.4358\times {10}^b$, then $b=$_____.

If the standard form of $26800005=2.6800005\times {10}^k$, then $k=$_____.