Answer:
68 readings.
Explanation:
We need to take this problem as a statistic problem where the normal distribution table help us.
We can start considerating that X is the temperature of the solution, then



For a confidence level of 90% our
is 1.645
Therefore,

Substituting for
and re-arrange for n, we have that n is equal to




We need to make 68 readings for have a probability of 90% and our average is within 
Light waves travel in straight lines when they are travelling in a uniform medium. This is because the waves are travelling at the same speed.
Answer:
decrease
Explanation:
Addition of a lubricant such as oil to a surface will decrease friction. This makes the surface more greasy or slippery. This is very much efficient in machines, for example.
The shock wave from the meteoroid in the lower atmosphere has a Mach angle of 0.948°.
(a) The meteoroid's speed 

Air sound wave speed 
Speed of the shock wave in Mach 

Hence, 0.948° is the Mach angle of the shock wave from the meteoroid in the lower atmosphere.
<h3>What is the speed of the meteoroid?</h3>
A meteoroid's speed can be loosely broken down into three categories: slow, medium, and fast.
- Slow meteors move around the sun at a leisurely pace of about 32 kilometers per second (20 miles per second).
- Medium-speed meteors travel around the sun at approximately 50 kilometers per second (30 miles per second),
- while fast meteors zoom past at over 120 kilometers per second (75 miles per second)!
To learn more about meteoroid, visit:
brainly.com/question/1939309
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