Answer:
4pi in^2
Step-by-step explanation:
Lateral surface area of a cylinder = 2πrh
π = pi
r = radius
h = height
Let me illustrate with an example
A cylinder has the following dimensions
r = radius = 20
h = height = 10
lateral area = 2 x π x 20 x 10 = 400π
If dimensions are reduced to one-fifth their original length, new dimensions are
r = radius = 20 x 1/5 = 4
h = height = 10 x 1/5 = 2
New lateral area = 2 x 4 x 2 x π = 16π
change in lateral area = 400π / 16π = 25
If dimensions are reduced by 1/5, lateral area would reduce by 25
100 pi / 25 = 4
x/4 = 3/2
x/2 = 3 (multiply both sides by 2)
x = 6 (multiply both sides by 2)
Therefore 6/4 = 3/2
Answer:
Area = 370 m²
Cost to paint = £105
Step-by-step explanation:
Area of the wall of a cinema hall = Area of a trapezoid (1)+ Area of a rectangle (2) + Area of a trapezoid (3)
Area of a trapezoid =
where
and
are the parallel sides and h is the distance between these sides.
Area of trapezoid (1) = 
= 69 m²
Area of the rectangle (2) = Length × Width
= 12 × 15
= 180 m²
Area of the trapezoid (3) = 
= 121 m²
Now area of the wall = 69 + 180 + 121
= 370 m²
One tin covers the area = 25 m²
Number of tins required to paint the wall = 
= 
= 14.8
Therefore, number of tins to be purchased = 15
Cost to paint the complete wall = 15 × £7
= £105
Answer:
21
Step-by-step explanation:
-(-26) would be positive 26 because one negative multiplied by another negative equals a positive. We are left with -5+26 which would equal 21.