What should be added to 63.47 to get 91?

Let the required number be x

63.47 + x = 91

x = 91 - 63.47

Converting the given decimals into like decimals, we have to subtract 63.47 from 91.00.

Subtracting columnwise, we get:

$\begin{array}{r} 91.00 \ -63.47 \ \hline 27.53 \ \hline \end{array}$

Hence, the answer is 27.53