use the full calculator readout when you do it the first time for the second time.. most calculators have a ANS button. use that..
then for your finally answer, if it doesn't state to how many d.p's then do it too 2
The answer is only accurate to the given significant figures so maybe like 3 sig. fig. is good enough. the marker is looking for whether you can use the formula or not rather than how many decimals you can write.