10.Find the smallest number that is divisible by each of the numbers 8, 15 and 20.

The smallest number divisible by 8, 15 and 20 is equal to their LCM.
\(\qquad \begin{array}{c|lcr} 2 & 8 \;,\;15\;,\;20\\ \hline 2 & 4 \;,\;15\;,\;10\\ \hline 2 & 2 \;,\;15\;,\;5\\ \hline 3 & 1 \;,\;15\;,\;5\\ \hline 5 & 1 \;,\;5\;,\;5\\ \hline & 1\;,\;1\;,\;1\\ \end{array} \)

LCM =\( 2 \times 2 \times 2 \times 3 \times 5 = 120\)

Here, 2, 3 and 5 have no pair.So they are multiplied to get the least number divisible by 8,15 and 20.

The required smallest square number =\( 120 \times 2 \times 3 \times 5 = 120 \times 30 = 3600\)