### The average of x1, x2, x3 and x4 is 16. Half the sum of x2, x3, x4 is 23. What is the value of x1?

A. 17 B. 18 C. 19 D. 20 Answer: Option B

### Solution(By Apex Team)

$\begin{array}{l}\mathrm{x}_1+\mathrm{x}_2+\mathrm{x}_3+\mathrm{x}_4=16\times4=64\\ \Rightarrow\frac{1}{2}\left(\mathrm{x}_2+\mathrm{x}_3+\mathrm{x}_4\right)=23\\ \Rightarrow\mathrm{x}_2+\mathrm{x}_3+\mathrm{x}_4=46\\ \therefore\mathrm{x}_1=64-46\\ \quad=18\end{array}$

A. 20
B. 21
C. 28
D. 32

A. 18
B. 20
C. 24
D. 30

A. 10 years
B. 10.5 years
C. 11 years
D. 12 years