Vedic Mathematics/Sutras/Urdhva-Tiryagbyham

< Vedic Mathematics/Sutras

Multiplication of a 2 figure integer $ab$ by another 2 figures integer $cd$ :

$\begin{array}{ccc}a& & b\\ |& \times & |\\ c& & d\\ a*c& ad+bc& b*d\end{array}$

or in base 10:

$(10a+b)(10c+d)=100(a*c)+10(ad+cb)+(b*d)$

of course, the cases where $(ad+cb)>10$ or $b+d>10$ are to be considered.