Math

In a month, the average time taken for four weekly club meetings was 1h 15 min. The total time taken for the first two meetings was 2h 5 min. What was the average time taken, in minutes , for the last two meetings?

$\begin{array}{rcl} \frac{m_1+m_2+m_3+m_4}{4} &=& 1\ h ~15\min.\\ \\ \hline \\ m_1+m_2 &=& 2\ h ~5\min.\\ \frac{m_1+m_2}{2 } &=& 1\ h ~2.5\min.\\ \\ \hline \\ \frac{m_3+m_4}{2 } &=& (\frac{m_1+m_2+m_3+m_4}{4})\cdot 2 - \frac{m_1+m_2}{2 }\\ &=& \frac{m_1+m_2}{2 }+\frac{m_3+m_4}{2 }- \frac{m_1+m_2}{2 }\\ \frac{m_3+m_4}{2 } &=& ( 1\ h ~15\min.)\cdot 2 -1\ h ~2.5\min.\\ \frac{m_3+m_4}{2 } &=& 2\ h ~30\min. -1\ h ~2.5\min.\\ \frac{m_3+m_4}{2 } &=& 1\ h ~27.5\min.\\ \frac{m_3+m_4}{2 } &=& 87.5\min.\\ \end{array}$

The average time taken, in minutes , for the last two meetings was 87.5 min.