Volumes help ! (1 Viewer)

[iampeterr]

Can anyone help me with this questions?

Find the volume of a right pyramid of height 10cm standing on a rectangular base whose dimensions are 8 cm and 6cm?

 

[barbernator]

well the volume for any rectangular pyramid is V=bhl/3= 8x6x10/3=160cm^3

 

[iampeterr]

i think you mean 160cm^3.

 

[barbernator]

i think you mean 160cm^3.

yeh

 

[iSplicer]

i think you mean 160cm^3.

I think you also forgot to thank barbernator for his help =)

 

[math man]

In 4u you are not allowed to do it
Directly like that, you should remember
That in 4u it's about understanding where
The volume comes from, ie, you have to
Derive the volume by taking slices and
Summing them up, say this question is
Worth 4 marks well then 2 marks will be
For deriving the volume integral and 2 more
Marks for getting the final answer, it could
Only be worth one mark. However the benefit
Of using the formula is to check that your
Answer by deriving it is the same

 

[SpiralFlex]

In 4u you are not allowed to do it
Directly like that, you should remember
That in 4u it's about understanding where
The volume comes from, ie, you have to
Derive the volume by taking slices and
Summing them up, say this question is
Worth 4 marks well then 2 marks will be
For deriving the volume integral and 2 more
Marks for getting the final answer, it could
Only be worth one mark. However the benefit
Of using the formula is to check that your
Answer by deriving it is the same

That's exactly what I thought.

 

[barbernator]

sorry guys, I haven't done volumes yet so i just answered it the way i knew how.

 

[math man]

 

[math man]

note here that every slice parallel to the base is a rectangle. At a height h, the lengths i let be x and y, and the slices thickness changes with respect to h, so i need to
put x and y in terms of h. and obv h varies from 0 to 10.

 

[Sanical]

In 4u you are not allowed to do it
Directly like that, you should remember
That in 4u it's about understanding where
The volume comes from, ie, you have to
Derive the volume by taking slices and
Summing them up, say this question is
Worth 4 marks well then 2 marks will be
For deriving the volume integral and 2 more
Marks for getting the final answer, it could
Only be worth one mark. However the benefit
Of using the formula is to check that your
Answer by deriving it is the same

lol I thought you wrote a poem

 

[iampeterr]

ah thanks guys !