A. The expression for the time t it takes to jog 5 miles from the park as a function of r, we shall proceed as follows: time=(distance)/speed time=t distance=5 miles speed=(r) miles per hour plugging the values in the formula we get: t=5/(r)
b. <span> When you run back to the park, your average speed increases by 1 mph. Write an expression representing your new speed. </span>Given that on the way back, the speed increases by 1 mph, the expression representing new speed will be: initial speed=r mph new speed=r+1=(r+1) mph
c. <span> Write an expression for the time t(in hours) it takes to jog 5 miles back to the park. Here we shall use the formula: Time taken for the jog 5 miles back to the park will be given by: time=distance/speed distance=5 miles speed=(r+1) mph thus time=5/(r+1) hours
d. The expression for total jogging time will be given by: Total time=5/r+5/(1+r) =[5(1+r)+5r]/[r(1+r)] =[5+5r+5r]/[r(1+r)] =(5+10r)/[r(1+r)]
e] The total time of jogging given that r=4 mph will be: plugging r=4 in the answer from (d) we get: (5+10r)/[r(1+r)] =(5+10*4)/[4(1+4)] =(5+40)/(4(5)) =45/20 =2.25 hours</span>
We can solve it two ways, we´ll do it via physics: We know that: d=vt d=770km/h*15h d=11550km Now at 660km/h: t=d/v t=11550km/660km/h t=17,5h Math way: 770km/h→15h 660km/h→x So: (770*15)/660=x x=17,5h
