they are not testing us for these type of calculations ,but if it appears product will also be there(You can check previous years(2007) JEE paper where 2.303*273*.....=.....    was given)

and in genral accuracy for 2 decimal places or at most 3 is suff.

and for your info i can suggest you learn vedic multiplication it will definetly help you, where you can multiply BIG numbers easily safely and even in limited space)

hehe