zacismyname

Thanks I enjoy presenting them :)

$$11r+18=51$$

$$11r=33$$

$$r=3$$

You have to write it like this in the calculator: (-5)^2

$${\left(-{\mathtt{5}}\right)}^{{\mathtt{2}}} = {\mathtt{25}}$$

If you simply type -5^2 it takes it as -(5^2)

$${\mathtt{\,-\,}}\left({{\mathtt{5}}}^{{\mathtt{2}}}\right) = -{\mathtt{25}}$$

$$\frac{5}{8}\times\frac{-72}{1}$$

$$\frac{5\times{-72}}{8}$$

$$\frac{-360}{8}$$

$$-45$$

$$m=-475t+2650$$

Substitute $$[m=1500]$$

$$1500=-475t+2650$$

$$-1150=-475t$$

$$t\approx2.421$$

(0.421*60=25.26)

t is aproximately 2 hours and 25 minutes, so the most correct answer is A.

Good work!

. . . I didn't

Cost of 1 book = b

$$12b=25.20$$

$$b=\frac{25.20}{12}$$

$${\frac{{\mathtt{25.2}}}{{\mathtt{12}}}} = {\frac{{\mathtt{21}}}{{\mathtt{10}}}} = {\mathtt{2.1}}$$

So one book costs $2.10

if I'm not mistaken you could be trying to find the volume of a sphere.

$${\frac{{\mathtt{4}}}{{\mathtt{3}}}}{\mathtt{\,\times\,}}{\mathtt{\pi}}{\mathtt{\,\times\,}}{{\mathtt{3}}}^{{\mathtt{3}}}$$

$${\frac{{\mathtt{4}}}{{\mathtt{3}}}}{\mathtt{\,\times\,}}{\mathtt{\pi}}{\mathtt{\,\times\,}}{\mathtt{27}}$$  Now put this into your calculator to get . . .

113.0973 (4 d.c.p.) cubed units

In short, dividing by 1/3 = multiplying by 3.

Look at this example. . . 

$${\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{2}} = {\mathtt{8}}$$

$${\frac{{\mathtt{4}}}{\left({\frac{{\mathtt{1}}}{{\mathtt{2}}}}\right)}} = {\mathtt{8}}$$  

$${\frac{{\mathtt{4}}}{{\mathtt{0.5}}}} = {\mathtt{8}}$$

See how there are 8 0.5's in 4?

Look at this also . . .

$$\frac{1}{2}\times{\frac{4}{5}=\frac{4}{10}=\frac{2}{5}$$

$${\frac{\left({\frac{{\mathtt{1}}}{{\mathtt{2}}}}\right)}{\left({\frac{{\mathtt{5}}}{{\mathtt{4}}}}\right)}}$$=$$\frac{1}{2}\times{\frac{4}{5}=\frac{4}{10}=\frac{2}{5}$$

Instead of dividing by a fraction we flip the denomonator and numerator and then multiply by the fraction. Notice how 3 can be written as 3/1, which when it is flipped is 1/3.

Also when you are dividing by a third, you are seeing how many thirds go into a number, so it makes sense that there are 3 times more thirds in a number than 1's, because 1/3 goes into 1 3 times. 1/1 can be written as 3/3.

I may have overcomplicated this/been confusing but I hope I helped :)