i'm using Hashcat for a while & try to solve this challenge: is this possible to crack at least half the possibilities combinations password of 10 character using 94 characters from keyboard with md4 hashing. I calculated & there 53,861,511,409,489,970,176 combinations, there was a service that offer using 2petaflops supercomputer for free, how fast would it be if i run on it?
Yes, it's possible and it can even be done relatively fast.
Any High End Radeon manufactured in the last years (anything since 5870 forward (and above at performance) but preferably RX580/570 or Vega) or the 1070/1080 series (even 1060 can do relatively good). A good performance reference is for the card to have at least 2T-FLOPs processing power (which all mentioned ones have).
If we take the example of the minimum I stated: Radeon 5870 - near full processing power will try the number of combinations you stated (53E) in approx 283 days. A 1060 half that. One RX580 1/3 that (<95 days). 4xRX580 can do it in under 25 days.
If you use more cards you get less time.
And since 2 TerraFLOPs can do it in 283 days, 2 PetaFLOPs (that you mentioned as a service) can do it in 0.276 days - aka under 7 hours.
Note: the above assumes a good software is used that can take advantage of near the full processing power of a card.
Note 2: For only half of your stated value, of course, only have the specified time will be required.