170 



FARM ARITHMETIC. 



what rate up a 5 per cent grade? Down a 5 per cent 

 grade? Down a 10 per cent grade? 



603. If in the preceding problem the team is required 

 to wallc at the rate of 2^/^ miles an hour up a 5 per cent 

 grade, what portion of the time should it be allowed to 

 rest? 



Measuring a Grade. 



The slope of a grade may be easily determined by 

 means of a level and a rule. A board resting along the 

 grade will facilitate the measurement. The level should 



How TO Measure Grade with Level and Rule. 



be placed in horizontal position, with one end resting on 

 the board or ground and the other pointing in the direc- 

 tion of the slope. With the rule measure the vertical 

 distance between the lower edge of other end of the level 

 and the board or ground. The ratio of this distance to the 

 length of the level is the slope of the grade. If the slope 

 be multiplied by 100 the per cent of the grade is obtained. 



604. In the above figure the level is 24 inches long and 

 the vertical distance is 2}i inches. What is the per cent 

 grade ? Slope ? 



605. Determine approximately some of the grades on 

 the roads in your vicinity. What is the steepest grade 

 over which you must haul in going to market? 



