Acontractor is mixing concrete and mixed 3 parts concrete and 9 parts water. how much water is needed for 12 parts concrete?

36 parts water

Step-by-step explanation:

3/9 = 1/3 = for every 1 part concrete, it's 3 parts water.

12/x = 1/3; x = 36

so, 12 x 3 = 36

since the airplane is moving with constant speed then the distance travelled can be calculated by x=u*t

in km/h would be:

x=640*3.5=2.240 km

in m/s would be:

u=640 km/h= 640.000 m/h =640.000/ 3600 m/s =177.8 m/s

t= 3.5 h= 3.5 * 3600 s=12.600 s

then x=u*t= 177.8*12.600= 2.240.280 m