Discrete random variable

A discret random variable X has the following probability distribution: 1,1,2,3,4,5,6,7P(X):,c,2c,2c,3c,c^(2),2c^(2),7c^(2)+ Find the value of c. Also,find the mean of the distribution.

The random variable X is the amount of syrup prescript by a physician. Then the random variable is

If the variance of the random variable X is 5 ,then variance of the random variable -3X is

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Number of floors in a building. Then the random variable is

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Number of attempts required by a candidate to clear I.A.S. examination. Then the random variable is

Number of students present in a class of 50 students Then the random variable is

A random variable X takes the values 0,1 and 2 .If P(X=1)=P(X=2) and P(X=0)=0.4 ,then the mean value of the random variable X is