Question

11
I wish to repaint the walls of my garage. It is 3 metres high, 4 metres wide and 9 metres deep. I
shall not need to paint the electronic door which covers one 3 x 4 metre end, nor the window, which
is 2 metres wide and 1 metre high, nor the rear door which is 1 metre wide and 2 metres high. 1
litre of paint covers 3 square metres.
How many 1 litre tins will be needed to complete the painting?

Answer 1

Answer:

33 tins

Step-by-step explanation:

4*9=36 m^2 - the ceilling

2*(9+4)*3 the walls

you have to paint 4*9+2*(9+4)*3-(3*4+2*1+1*2)=36+78-16=98 m^2

98<99

99:3=33 l will be needed

Answer 2

45 tins will be needed.

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To solve this question, the surface area of a rectangular prism need to be found. With the surface area that will be painted, it is possible to find the number of 1 liter tins that will be needed.

Surface area:

The surface area of a rectangular prism with height h, width w and depth d is:

$S = 2(hw + hd + dw)$

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Total surface area:

• 3 meters high means that $h = 3$
• 4 meters wide means that $w = 4$
• 9 meters deep means that $d = 9$

Thus, the total surface area, in square meters, will be:

$S = 2(3\times4 + 3\times9 + 4\times9) = 150$

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Area painted:

These following areas will be removed:

• One 3x4 end;
• A 2x1 end;
• A 1x2 end;

Thus, the total area painted will be:

$S_p = 150 - (3\times4 + 2\times1 + 1\times2) = 134$

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How many tins?

• One liter paints 3 square meters.
• There are 134 square meters.

Thus:

$\frac{134}{3} = 44.67$

Rounding up:

45 tins will be needed.

A similar question is given at https://brainly.com/question/24332238