Datediff to get a month year in decimal

So this is what i have:

CAST(DATEDIFF(month, a.LstPaymentDte, a.createdte)/12 as DECIMAL(10, 1)) AS diff_in_month

Example: a.LstPaymentDte = 6/13/2019 and createdte = today

I want the value output to show 1.1, so the year would be 1 and the month would be .1

Any thoughts on what I need to do?