Q: Convert 40 mm pipe diameter to inches.

The correct answer is: $1.5748031496\text{ in}$ Explanation We use the exact conversion factor $1\text{ in}=25.4\text{ mm}$. Steps: Convert millimetres to inches: $$\text{inches}=\frac{40\text{ mm}}{25.4\text{ mm/in}}$$ Compute the division: $$\text{inches}=\frac{40}{25.4}=1.5748031496\text{ in}$$ Rounded to a practical number of decimals: To three decimals: $1.575\text{ in}$ To two decimals: $1.57\text{ in}$ Therefore, 40 mm ≈ $1.5748\text{ in}$ (about $1.575\text{ in}$). Note: If you mean nominal pipe size (common plumbing/pipe terms), the nominal inch sizes do not always equal the actual outside diameter; tell me the context if you need the nearest standard pipe size instead.

Q: what is standard form of 3x3x3x3

The correct answer is: $81$ Explanation This is repeated multiplication of 3 four times, which can be written using an exponent as $3^4$. Calculate step by step: Steps: First step: $$3\times3=9$$ Second step: $$9\times3=27$$ Final step: $$27\times3=81$$ Therefore, $3^4 = 81$.

Q: What is the formula to find the total surface area?

The formula depends on the 3D shape. Here are the total surface area (TSA) formulas for common solids: Cube: TSA = $6a^2$ (where $a$ is the edge length) Rectangular prism (box): TSA = $2(ab + bc + ac)$ (edges $a,b,c$) Sphere: TSA = $4\pi r^2$ (radius $r$) Right circular cylinder: TSA = $2\pi r^2 + 2\pi r h$ (two circular bases plus curved surface; radius $r$, height $h$) Right circular cone: TSA = $\pi r^2 + \pi r l$ (base area $+\,$lateral area; $r$ = base radius, $l$ = slant height) Right prism (general): TSA = $2B + Ph$ (where $B$ = area of one base, $P$ = perimeter of the base, $h$ = prism height) Pyramid (regular or not): TSA = $B + \tfrac{1}{2}Pl$ (base area $B$, perimeter of base $P$, slant height $l$) Hemisphere: curved surface = $2\pi r^2$; including base (flat face) TSA = $3\pi r^2$. If you meant a specific solid, tell me which one and I’ll show a worked example.

Q: 30% of 900

The correct answer is: $270$ Explanation Thirty percent means thirty per hundred, so 30% of a number equals 0.3 times that number. Multiplying 0.3 by 900 gives the result. Steps: First step: $$30\% = \frac{30}{100} = 0.3$$ Second step: $$0.3 \times 900 = 270$$ Final step: $$\text{Therefore, }30\%\text{ of }900\text{ is }270.$$ Therefore, 30% of 900 is 270.

Q: What is 5 over 6 divided by 8?

The correct answer is: $\frac{5}{48}$ Explanation You divide by 8 by multiplying by its reciprocal (1/8). That gives a product of two fractions which you multiply across numerator and denominator. Steps: First step: $$\frac{5}{6}\div 8 = \frac{5}{6}\times\frac{1}{8}$$ Second step: $$\frac{5\times1}{6\times8} = \frac{5}{48}$$ Final step: $$\frac{5}{48}\text{ (cannot be simplified further)}$$ Therefore, $ \frac{5}{6} $ divided by $ 8 $ equals $ \frac{5}{48} $ (approximately $0.1041667$).

Q: Why is the value of k taken as 9×10

The short answer: Because $k$ is Coulomb's constant, defined by $k=\dfrac{1}{4\pi\varepsilon_0}$, and using the measured permittivity of free space gives $k\approx8.99\times10^9$, which is rounded to $9\times10^9$ for simplicity. Explanation Coulomb's law for the electrostatic force between two point charges is usually written as $$F=k\frac{q_1q_2}{r^2}.$$ The constant $k$ is related to the permittivity of free space $\varepsilon_0$ by $$k=\frac{1}{4\pi\varepsilon_0}.$$ The measured value of the vacuum permittivity is $\varepsilon_0\approx8.854187817\times10^{-12}\text{ F/m}.$ Plugging this into the formula gives $$k=\frac{1}{4\pi(8.854187817\times10^{-12})}\approx8.98755179\times10^9\text{ N·m}^2\text{/C}^2.$$ For most textbook and classroom work this is rounded to a convenient value: $$k\approx9\times10^9\text{ N·m}^2\text{/C}^2.$$ The rounding makes calculations easier and the small difference (about 0.14%) is negligible in typical problems. Why that particular number? The numerical value comes from the chosen SI units (meter, kilogram, second, ampere) and the experimentally measured $\varepsilon_0$. Conceptually, $\varepsilon_0$ and hence $k$ arise from the way the electric field behaves in free space (Maxwell’s equations). The value is not arbitrary — it is determined by measurements and the SI system. If you’d like, I can show the numeric substitution step-by-step or explain how the value connects to other constants (e.g., the speed of light and magnetic constant).

Question

Convert 40 mm pipe diameter to inches.

Accepted Answer

The correct answer is: $1.5748031496	ext{ in}$

Explanation

We use the exact conversion factor $1	ext{ in}=25.4	ext{ mm}$.

Steps:

Convert millimetres to inches: $$	ext{inches}=\frac{40	ext{ mm}}{25.4	ext{ mm/in}}$$
Compute the division: $$	ext{inches}=\frac{40}{25.4}=1.5748031496	ext{ in}$$
Rounded to a practical number of decimals:

To three decimals: $1.575	ext{ in}$
To two decimals: $1.57	ext{ in}$

Therefore, 40 mm ≈ $1.5748	ext{ in}$ (about $1.575	ext{ in}$).

Note: If you mean nominal pipe size (common plumbing/pipe terms), the nominal inch sizes do not always equal the actual outside diameter; tell me the context if you need the nearest standard pipe size instead.