The wall is in the shape of a rectangle. The wall is 3 m wide and 2.5 m high.
The tiles are rectangles 20 cm wide and 25 cm high.
The tiles are sold in boxes.
There are 20 tiles in each box.
Each box of tiles costs £8.50
Work out the total cost of the boxes of tiles Andy needs to buy.
You must show all your working.
(Hint: First find the area, then find the number of tiles needed

Step-by-step explanation:

Area of wall (including window ) 4.5×3=13.5m

2

Area of window is 80×50+

2

1

×80×20

4000cm

2

+800cm

2

=4800cm

2

=0.48m

2

Area needed to paint 13.5−0.48=13.02m

2

Cost of painting=13.02×158=2057.16

the value of v.w= -12.

step-by-step explanation:

we are given three vector r,v and w as:

r = < 5, -5, -2> ; v = < 2, -8, -8> ; w = < -2, 6, -5>

we know that r,v and w could also be represented as:

r=5i-5j-2k

v=2i-8j-8k

and w= -2i+6j-5k

where i,j and k are the unit vectors of x,y and z-axis respectively.

also we know that it has the following property:

i.i=1 ; j.j=1; k.k=1

and i.=j.i=i.k=k.i=j.k=k.j=0

i.e. when we multiply two vectors or we find it's dot product we need to only multiply the components of x coordinates with each other; y with each other and z with each other.

hence, v.w= (2i-8j- -2i+6j-5k)

                  = 2×(-2)+(-8)×(6)+(-8)×(-5)

                  = -4-48+40

                  = -12

hence, v.w= -12