Hi PrepLounge community,

I have seen crazy records in the 'Mental Maths' section of PrepLounge and I would really appreciate some clarification.

What is the expectations for fast maths in MBB? This is my current situation after some training:

- I can perform quite well mentally all the
**basic calculations**: - Additions and subtractions up to three digits (e.g. 365 - 174) - Basic multiplication that include 25/75/50/100 - Basic fractions - 'Ballpark' calculations --> In maximum 10 seconds and with a low percentage of mistakes (hopefully!) - Yet, I need to write down (as I did in elementary schools) the
**toughest calculations**- Additions and subtractions of 5+ items, or 4+ digits - Toughest fractions - Divisions by two-plus digits - Multiplications by two-plus digits without easy shortcuts --> I can do this in maximum 30 seconds, but it's still writing down while the interviewer knows the final number.

1) Is this normal?

2) And how can I better 'manage' the toughest calculations from a communication perspective: I don't want to lose track of the interviewer, but I need to regroup and focus on the on-paper calculations?

Thank you so much!

Anonymous