It is customary to work in SI units.
Calculate the volume of the concrete.
V = 3.7*2.1*5.8 cm³ = 45.066 cm³ = 45.066 x 10 ⁻⁶ m³
The mass is 43.8 g = 43.8 x 10⁻³ kg
The density is mass/volume.
Density = (43.8 x 10⁻³ kg)/(45.066 x 10⁻⁶ m³) = 971.9 kg/m³
Answer: 971.9 kg/m³
Answer:
The force of gravity exerts a downward force. The floor exerts an upward force. Since these two forces are of equal magnitude and in opposite directions, they balance each other.
Answer:
Significant digits (also called significant figures or “sig figs” for short) indicate the precision of a measurement. A number with more significant digits is more precise. For example, 8.00 cm is more precise than 8.0 cm.
Im not 100% sure you have to tell me if im wrong or not.
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Answer:
Average speed will be 48.23 km/h
Explanation:
Let the distance up to hill is = d km
Speed when car goes to hill = 38 km/h
So time required 
Speed when car return from hill = 66 km/h
So time required to return fro hill 
Total time 
Total distance = d+d =2d
So average speed
