SG. 4 Find $Q$ if the sum of the numbers in the $100^{\text {th }}$ group is $100 Q$.
The last number in the $100^{\text {th }}$ group $=2(1+2+\ldots+100)=2 \cdot \frac{1}{2} \cdot 100 \cdot(1+100)=10100$ The first number of the $100^{\text {th }}$ group $=10100-2(100-1)=9902$
$$
\begin{array}{l}
9902+9904+\ldots+10100=100 P \\
\frac{1}{2} \cdot 100 \cdot(9902+10100)=100 P \\
P=10001
\end{array}
$$