how to find the square of 15 and 16???

Dear Student,

Please find below the solution to the asked query :

$$\begin{gathered} \left(\mathrm{a}\right). \\ {15}^2 = {\left(10+5\right)}^2 = {10}^2 + 5^2 + 2\times 10\times 5 = 100+25+100 = 225 \\ \left(\mathrm{b}\right). \\ {16}^2 = {\left(10+6\right)}^2 = {10}^2 + 6^2 + 2\times 10\times 6= 100+36+120= 256 \end{gathered}$$

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