Three fair coins numbered 1 and 0 are tossed simultaneously. Then variance Var (X) of the probability distribution of random variable X, where X is the sum of numbers on the uppermost faces, is
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Logic Tip: Tossing a coin with '0' and '1' faces is exactly a Bernoulli trial. For $n=3$ tosses with success probability $p=0.5$ (getting a '1'), the distribution is Binomial $B(3, 0.5)$. The variance of a binomial distribution is simply $npq = 3 \times 0.5 \times 0.5 = 0.75$. This shortcut bypasses all tabular calculations!