Ablock of height 120mm is placed on top of another block with a height of 1.50 m. what is the height of the two blocks together? (1000mm = 1m) a) 1.72 m b) 1.62 m c) 2.70 m d) 121.5 m

We will first convert all units to meters and then solve the problem.
We are given that:
1000 mm = 1 m
120 mm = ?? meters
using cross multiplication:
120 mm = (120*1) / 1000 = 0.12 m

Now, when the two objects are placed over each other, their total height is the result of summation of both heights, therefore:
total height = 0.12 + 1.5 = 1.62 m

Based on the above calculations, the correct choice is:
b) 1.62 m 

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Answer sample (c); // would be best because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the smallest;