FARM MECHANICS. 169 



596. What per cent is a grade having a rise of 2^ 

 feet in 80 feet? Of 53 feet in a mile? Two inches in 2 

 feet? 



597. In a 3 per cent grade what is the rise in 800 feet ? 

 What distance down the grade would give a fall of 15 

 feet? 



For grades less than 20 per cent a very good approxi- 

 mate rule for calculating the draft is the following: 



The draft up a grade whose per cent is known is equal 

 to the draft on the level, increased by a quantity which 

 is equal to the grade per cent of the total weight of 

 the load. The draft down a grade is .equal to the draft on 

 the level decreased by this quantity. 



598. The draft of a total load of 3,000 pounds on a 

 certain level road is 200 pounds. What is the draft on a 

 4 per cent grade on the same road ? 



Process : 



3,000 X -04 = 120 



200 -f 120 = 320 pounds draft up grade. 

 200 120 = 80 pounds draft down grade. 



599. In the above problem suppose the grade to be 

 10 per cent, find the draft up grade. What would be the 

 draft in going down this grade? 



600. A total load of 4,500 pounds has a draft on a cer- 

 tain level road of 100 pounds per ton. What is the draft 

 up a 3 per cent grade ? Down a 5 per cent grade ? Up a 

 12 per cent grade ? Down a 12 per cent grade ? 



601. If a 2,500-pound load is found to have 150 

 pounds draft on a certain level road, what is the per cent 

 grade -down which the draft will be zero ? What will be 

 the draft up this grade ? 



602. At what rate may a team of 1,500-pound horses 

 draw a load, including the wagon, of two tons on a level 

 road when the total draft is 160 pounds per ton? At 



