D DRAWING TO SCALE c 312. Definition of Scale. Drawings are frequently made so that a certain unit of length such as one inch in the drawing will represent a definite distance, such as one foot, or 10 feet, or one mile in the object represented by the drawing. If one inch in the drawing represents 10 feet or 120 inches in the object, then the drawing is said to be to the scale 1:120. This is read "scale one to one hundred twenty." A Scale 1: 10' B This scale is also written 1": 10', which is read "scale: 1 inch to 10 feet.' PROBLEMS 1. What are the dimensions of the room represented by this figure? 2. The top of a certain desk is 5 feet long and 3 feet wide. Make a drawing of the top of this desk to the scale 1: 12. 3. Make a drawing of the same desk to the scale 1": 2'. Express this scale without using the words " inches" and "feet " in the statement. 4. What is the straight line distance from A to C in the room represented by the figure above? 5. Measure a room in the school building with care, and make a drawing to scale representing it. Enter the scale on the drawing. 6. Measure the dimensions of a room in your home, and make a drawing to scale representing it. 7. Determine the dimensions of a football field by measuring the drawing given on page 247 and then computing them. The points G H and E F mark the goal posts. Determine approximately the distance between each pair of goal posts. 8. Draw a football field to the scale 1": 30'. 9. Express the scale of Example 8 without using the words inches and feet. 10. Determine the dimensions of a tennis court by measuring the drawing given here and then computing them. Give the lengths of the lines AB, BC, GO, FH, HI. 11. A baseball diamond is a square ninety feet on each side. The pitcher's box is in a straight line between first and third bases and also in a straight line between the home plate and second base. Draw a baseball diamond to the scale 1": 10'. MISCELLANEOUS WORK 1. Five loads of corn weigh as follows: 3120, 2840, 3486, 2952, 2662 pounds. The tares are: 1140, 1080, 1250, 1168, 1286 pounds. Find the value of the corn at 56 é a bushel. 2. A commission merchant bought 1960 pounds of flour at $5.60 a barrel; 10 barrels of salt at a pound; 1750 pounds of pork at $16 a barrel. What did the whole cost him? 3. Divide 17 tons 875 pounds of coal equally among 9 families. 4. A grocer mixes two kinds of tea as follows: 676 pounds 10 ounces Salada with 590 pounds 12 ounces English breakfast. He sells from the mixture 457 pounds. What is the balance worth at 50¢ a pound? 5. At $7.50 a ton find the value of of a ton. 6. What part of a pound avoirdupois is a pound troy? A pound apothecaries'? 7. If one ring weighs 10 grains, how many such rings can be made from a pound of gold? 8. From of a long ton take of a long hundredweight. 9. Find the total value of 3650 lb. of wheat at $1.15 per bushel. 3780 lb. of wheat at $1.20 per bushel. 3560 lb. of wheat at $1.18 per bushel. 10. Find the total value of 2160 lb. of hay at $14.50 per ton. 2230 lb. of hay at $14.50 per ton. 2060 lb. of hay at $14.50 per ton. 2140 lb. of hay at $14.75 per ton. CHAPTER XX SPECIFIC WEIGHT 313. Certain objects will float on water while others sink in it. This is because some objects are lighter than water, while others are heavier. Thus nearly all kinds of wood are lighter than water and hence float on it, while nearly all rocks and metals are heavier than water and hence sink in it. 314. Specific Weight. The ratio of the weight of a certain volume of a substance to the weight of the same volume of water is the specific weight of the substance. Thus, one cu. ft. of cork weighs 15 lb. while one cu. ft. of water weighs 62.5 lb. Hence the specific weight of cork is Again, one cu. ft. of steel weighs 489.6 lb. 15 62.5 = .24 (approximately). Hence its specific weight is 489.6 62.5 = - 7.834 (approximately). WRITTEN EXERCISES Find the specific weight of each of the following, the weight of one |