$\text{ If }{\mathrm{a}}_1,{\mathrm{a}}_2,{\mathrm{a}}_3\dots \text{ is an A.P such that }{\mathrm{a}}_1+{\mathrm{a}}_5+{\mathrm{a}}_{10}+{\mathrm{a}}_{15}+{\mathrm{a}}_{20}+{\mathrm{a}}_{24}=225\text{ then }$${\mathrm{a}}_1+{\mathrm{a}}_2+{\mathrm{a}}_3+\dots +{\mathrm{a}}_{23}+{\mathrm{a}}_{24}\text{ is }$

${\mathrm{a}}_1+{\mathrm{a}}_5+{\mathrm{a}}_{10}+{\mathrm{a}}_{15}+{\mathrm{a}}_{20}+{\mathrm{a}}_{24}=225$

$\begin{array}{l}\Rightarrow 3\left(a_1+a_{24}\right)=225 \left(sum of n terms in A.P=\frac{n}{2}\left(a+l\right)\right)\\ \Rightarrow a_1+a_{24}=75\\ a_1+a_2+a_3+\dots +a_{24}=\frac{24}{2}\left[a_1+a_{24}\right]=12\left(75\right)=900\end{array}$