Times 2 Jumbo Quick 1146

[dofray]

Help required to help me finish the easy jumbo crossword and then let me start the cryptic one. Thanks for any help given.
34d Reduction in density (of a gas) (11). R???P???I?N
39a Something old fashioned (8). ???H?I?? Is this ARCHAISM?
42d Approximate calculation (8). ?U???A?E. Could this be GUESSAGE
Over to all you clever people........ It could be that some letters are wrong but am sure you will put me right.

[dannyk13]

34d.Rarefaction

[bibblebub]

rarefaction
archaism
estimate

[dofray]

Thank you dannyk13 and bibblebub for the answers looks like I have something wrong with 44a I thought it was group participation but it can't be. Thinking head on now.

[bibblebub]

don't get angry (hint) when you suss it

[MargoTester]

Cross fertilisation

[dofray]

Thanks everyone so easy when you see it, now on to the cryptic . Hope you are all having a good day.