ARITHMETIC 313 



32 ft. wide, the walls being 24 ft. high and 2 l / 4 ft. thick? 

 There are 8 windows, each 5 ft. wide and 11 ft. high, 

 and 2 doors, each 6 ft. wide and 9 ft. high, (b) What 

 will be the cost of laying the walls at $3.50 per perch? 



SOLUTION. 



Length of wall (outside) = 2X60+2X32 = 184 ft. 



Actual length = 184 - 4 X 2 J = 175 ft. 



Actual cubical contents = 1 75 X24X2J = 9, 450 cu. ft. 



Allowance for windows = 5X 11X2^X8 = 990 cu. ft. 



Allowance for doors = 6X9X2^X2 = 243 cu. ft. 



Net contents = 9,450 -(990+243) =8,217 cu. ft. 



(a) Perches required for wall = 8 ,2 1 7 -i- 24 f = 332 . 



(6) Since, in estimating the cost of the work, no allowance 

 is made for corners, doors, and windows. 



Cubical contents = 184 X 24 X2i = 9, 936 cu. ft. 



Perches of stone work = 9, 936 -4- 24 f = 401 A- 



Cost of laying walls = 401 AX $3.50 = $1,405.09. 



BRICKWORK 



Brickwork is generally estimated by the thousand 

 bricks laid in the wall, but measurements by the cubic 

 yard and by the perch are also used. To allow for 

 mortar, l /4 in. is added to the length and to the thickness 

 in making calculations. The following data will be 

 found useful in calculating the number of bricks in a 

 wall. For each superficial foot of wall 4 in. in thickness 

 (the width of 1 brick), allow 7 l / 2 bricks; for a 9-in. wall 

 (the width of 2 bricks), allow 15 bricks; and so on, 

 estimating 7 l / 2 bricks for each additional 4 in. in thick- 

 ness of wall. If brickwork is to be estimated by the 

 cubic yard, allow 500 bricks to 1 cu. yd. This figure is 

 based on the use of 8^4 in. x 4 in. x 2^4 in. bricks, with 

 .mortar joints not over y$ in. thick. If the joints are 

 14 in. thick, as in face brickwork, 1 cu. yd. will require 

 about 575 bricks. In making calculations of the number 

 of bricks required, an allowance of, say, 5% should be 

 made for waste in breakage, etc. 



