Question

10 identical pipes fill water tank in 4h, 8 pipes fill the same tank in how many hours ?​

Answer 1

$\begin{gathered}10 - - - - - > 4 \\ 1 - - - - - - > 4 \times 10 = 40 \\ 8 - - - - - - > \frac{40}{8} = 5 \end{gathered}$