# Find the surface area of the water in the given prism

• chwala
In summary, the conversation was about a question regarding surface area and a mistake made in calculating it. The solution involved using similarity and significant figures.
chwala
Gold Member
Homework Statement
See attached ( past paper question)
Relevant Equations
Knowledge of prisms
My query in only on the highlighted part...c.ii.

Find the question below;

Find the markscheme here

part c(ii) does not seem correct as i have;
##A_1=0.5 ×(0.65+0.84)0.3 ×2=0.447m^2##
##A_2 = 0.65 ×1.6=1.04m^2##
##A_3 = (0.3146 × 1.6)2=1.00672m^2##
Total surface area = ##A_1+A_2+A_3=0.447+1.04+1.00672=2.494m^2##...

For part c.(i), i was able to use similarity (i used a right angle triangle from the cross-section) to show that,
i.e ##\dfrac {0.477}{0.15}##=##\dfrac {0.3}{x}##
##x=0.094## therefore, ##w = 0.65+2(0.094)=0.8386≈0.84## to 3 2 significant figures.

Last edited:
Delta2
aaargh! its the english man, i figured it out, ##0.84 × 1.6! ## Area of surface and not Surface area! phew

chwala said:
##x=0.094## therefore, ##w = 0.65+2(0.094)=0.8386≈0.84## to 3 significant figures.
0.8386 to 3 significant figures amounts to 0.839

(i.e. a leading zero does not count as a significant figure)

##\ ##

BvU said:
0.8386 to 3 significant figures amounts to 0.839

(i.e. a leading zero does not count as a significant figure)

##\ ##
...to two significant figures...yeah, i know that. cheers bvu...

## 1. What is the formula for finding the surface area of a prism?

The formula for finding the surface area of a prism is 2 times the base area plus the lateral area, which is the perimeter of the base multiplied by the height of the prism.

## 2. How do I find the base area of a prism?

To find the base area of a prism, you need to know the shape of the base. For example, if the base is a rectangle, you can find the area by multiplying the length and width. If the base is a triangle, you can use the formula 1/2 times the base multiplied by the height.

## 3. What is the lateral area of a prism?

The lateral area of a prism is the area of all the sides of the prism, not including the base. It is found by multiplying the perimeter of the base by the height of the prism.

## 4. Can I find the surface area of a prism if I only know the dimensions of the base?

No, you also need to know the height of the prism in order to find the surface area. Without the height, you cannot calculate the lateral area.

## 5. Is there a difference between the surface area and volume of a prism?

Yes, the surface area is the total area of all the sides of the prism, while the volume is the amount of space inside the prism. The volume is calculated by multiplying the base area by the height of the prism.

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