E(X)=∑XiP(Xi)=15×7526k=15263
⇒k=27
Substituting k=27, the values of X become:
X: 14, 15, 16, 17, 18, 19, 20, 21
P(X): 152, 151, 152, 51, 151, 152, 51, 151
P(X<20)=X=14∑19P(X)
=152+151+152+51+151+152=1511
The probability distribution of a random variable X is given below :
XP(X)4k152730k151732k152734k51736k151738k152740k516k151
If E(X)=15263, then P(X<20) is equal to :
Held on 28 Jan 2026 · Verified 6 Jul 2026.
1511
53
1514
158
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