Let length = x meters, then breadth = 0.6x 

Given that  perimeter = 800 meters 

=> 2[ x + 0.6x] = 800 

=> x = 250 m 

Length = 250m and breadth = 0.6 x  250 = 150m 

Area = 250 x 150 = 37500 sq.m

Area of the sheet =  20 × 30 c m 2  

Area used for typing =  20 - 4 × 30 - 6 c m 2   

required % = 384 600 × 100=64%

circumference of a circle = 2 ?r

=> 2 × 22/7 × r ? r = 37

=> 37/7 × r = 37

=> r = 7 cm.

Diameter D = 2r = 7×2 = 14 cm.

The triangle with sides 26 cm, 24 cm and 10 cm is right angled, where the hypotenuse is 26 cm.

Area of the triangle =1/2 x base x height => 1/2 x 24 x 10 = 120 sq.cm

Given length of the rectangle = 3 cm

Breadth of the rectangle = 4 cm

Then, the diagonal of the rectangle  D = 3 2 + 4 2 = 25 = 5

Then, it implies side of square = 5 cm

We know that Area of square = S x S = 5 x 5 = 25 sq.cm.

Given that length and area, so we can find the breadth.

 Length  x  Breadth = Area 

 => 20  x  Breadth = 680 

=> Breadth = 34 feet 

Area to be fenced = 2B + L = 2 (34) + 20 = 88 feet

Let the length be 'l' and breadth be 'b'.

b = l × 3/4__________(a)

2(l+b) = 1050

l+b = 525___________(b)

From equations (a) and (b),

l = 300m, b = 225 m

Area = l × b

= 300 × 225

= 67500 sq.m.

Let length, breadth and height of the room be 7, 3, 1 unit respectively.

Area of walls = 2(l+b)xh = 2(7+3)x1 = 20 sq. unit.

Now, length, breadth and height of room will become 3.5, 6 and 2 respectively. 

Area of walls = 2(l+b)xh = 2(3.5+6)x2 = 38 sq. unit. 

% Increase in the area of walls = (38-20)x100/20 = 90%.

Number of square units in 13 by 9 is given by the area it forms with length and breadth as 13 & 9

Area = 13 x 9 = 117

Hence, number of square units in 13 by 9 is 117 sq.units.

Area of the square = 1 2 * d i a g o n a l 2 = 1 2 * 3 . 8 * 3 . 8 = 7 . 22 m 2