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# HElp in C2 Maths mei papers watch

1. can anyone explain me the question ten part 1 and 3
coz the answer doesn't make any sense.

im doing a level maths and i got exam on month of may and june. in addition im doing mechanics which is similar to physics and makes me mad.

2. (Original post by Rockypete1)
can anyone explain me the question ten part 1 and 3
coz the answer doesn't make any sense.

im doing a level maths and i got exam on month of may and june. in addition im doing mechanics which is similar to physics and makes me mad.

10. (i) Find h in terms of x.

The volume of a cuboid is the base area times the height:

You also know that the volume of the cuboid is . Therefore:

Rearrange to make h the subject:

Hence show that the surface area, , of the cuboid is given by:

.

The surface area of the cuboid is the area of the six faces added together:

Substitute in h:

(ii) Find and .

(iii) Hence find the value of x which gives the minimum surface area.

The surface area is given by . To find the value of which gives the minimum surface area, you need to find the value of which gives the lowest value for , i.e. when and .

Equate to and solve for :

Substitute into to check that it does give a minimum value i.e. greater than :

Therefore gives a minimum value.

Find also the value of the surface area in this case.

Now we substitute the value for into the equation for the surface area, :

This can also be written as , which is much easier to substitute:

Use the laws of indices to simplify it:

Therefore rounding to 3 significant figures gives:

Phew; that was a hell of a lot faster to do with pen and paper!
3. thanks you so much for the answer.....

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