mobiles

I know mobile charges differ greatly depending on operator,time etc.But generally is it cheaper to ring a mobile to mobile(both 087) or a landline to mobile?(and vice versa)
thank you

Generally Yes - mobile to mobile within the same network provider is usually cheaper than mobile to landline.

Each operator lists or summarises their tariff plans on their website:

[broken link removed]
[broken link removed]
www.vodafone.ie/phonestar.../index.jsp

> is it cheaper to ring a mobile to mobile(both 087)

Note that mobile prefixes no longer necessarily denote the mobile operator. It used to be 085=Meteor, 086=O2, 087=Vodafone but since mobile number portability came in this is no longer the case:

Alternatively, from a landline, ring the appropriate [broken link removed] number (0818 270 101), wait for the voice prompt, dial your mobile number and press #, and pay for the call at Eircom's national rate — 8.17c/min daytime, 6.35c/min evenings and weekends...