Question: Using assume or assuming to eliminate added terms

I would like to be able to enter an assumption into maple indicating one variable is much greater than another.  I would then like maple to eliminate the smaller variable term when it is added together with the much greater term.  However when I use the >>> symbol in maple along with assuming I get an error. 

> eqn1 := y = a*t+b*t;
                         y = a t + b t
> solve(eqn1,y) assuming a>>>b;
Error, (in assuming) when calling 'assume'. Received: 'last object, `⋙`(a, b), has no property'
> eval(eqn1) assuming a>>>b;
Error, (in assuming) when calling 'assume'. Received: 'last object, `⋙`(a, b), has no property'

I would like to be able to indicate that a is 'much greater' than b, then have maple return something like this when using solve or eval:

y~=at,

eliminating the bt term.  Is this possible?