How to remove unwanted 000's in a Calculated Field result?

Hi there

I have painstakingly created a formula for a Calculated field and it's very nearly working...

The Formula is 

concat(toString(divide(number($pr_enquiry_initial_payment),number($pr_enquiry_monthly_payment)))," + ",toString(subtract(number($pr_enquiry_term),1)))
The result I get is: "9.000000 + 47.000000"
What would I need to change in the formula to make it just return "9 + 47" ?
Sorry if it's a stupid question - but I haven't written a formula in 20 years prior to getting this far on this one...
Thanks