The answer is C : 15.7 m/s
Use the idea of : momentum before collision = momentum after collision
Before collision;
For car:mass=1.1×10^3, velocity=22
For truck:mass=2.3×10^3, velocity=0
After collision;
For car:mass=2.3×10^3, velocity=-11
For truck:mass=2.3×10^3, velocity=V
(1.1×10^3 × 22) + (2.3×10^3 × 0) = (1.1×10^3 × -11) + (2.3×10^3 × V)
24200 = -12100 + 2.3×10^3V
2.3×10^3V = 36300
V = 15.7 m/s
Answer:

Explanation:
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In this case, when we want to balance chemical reactions such as in this case, the idea is to equal to number of atoms of each element at each side of the equation according to the lay of conservation of mass, just as shown below:

Because we have four phosphorous and ten oxygen atoms at each side.
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Manipulation of the independent variable should change the dependent variable, the value of which "depends" on the independent variable's change in value.
the average speed is 23.4 km per hour cause it is total distance over total time equal to average speed