Question 60562
Solution:
a)  The hiking club hiked to Robbers Cave State Park at 4 mph
     They got a ride back to town in a truck that went 20 mph.
     Formula: Total speed = total distance / total time.
     Total speed = (4 + 20) mph = 24mph
    Total time = 18hrs
   Substituting in the above formula, we have 
   24 = total distance / 18
   24 * 18 = total distance
  432 = total distance
  Distance from park to the town + distance from the town to park = 432
  Distance from park to the town =  distance from the town to park
  So we write it as,
 2 distance = 432
 Distance = 432 /2
 Distance = 216miles
 The distance from the park to the town is 216 miles. 

b) we use the similar concept to solve.
     Formula: Total speed = total distance / total time.
     5 + 20 = total distance / 10
     25 = total distance / 10
     25 * 10 = total distance
     250 = total distance
    Distance walked + distance came back to home = 250
    Distance walked = distance came back to home
    So we write it as,
    2 Distance walked = 250
    Distance walked = 250 /2
    Distance walked = 125 km

      c)    Let the number of girls be “x”
            And the number of boys be “y”
            Given that there are 6 more girls than twice the number of boys
            i.e. 6x = 2y
                  3x = y                --- (1)
            Also given there are 36, boys and girls in all.
            i.e.  x + y = 36         --- (2)
            Substituting equation (1) in equation (2), we get
            x + 3x = 36       
            4x = 36
            x = 9
            Now substitute the value of “x” in equation (1) we get
            3* 9 = y
            27 = y
            Therefore the number of girls are 9 and number of boys are 27