How to shorten Strings? (i.e. temperature from xx.yyyyyyyyyyyyyyyyyyyyyy to xx.y)

I use Netatmo go get the living room temperature. If i just use the item in the sitemap it displays the temperature as it should: xx.y°C.
But if i combine temperature and humidity into a new item using a rule, I get a whole bunch of digits behind, e.g. Wohnzimmer 24.8999996185302734375 °C / 63
How can i cut after the first digit to 24.8 oder even round to 24.9?

I use this rule:
rule “update Wohnzimmer”
Item WoZi_Temperatur received update or Item WoZi_Luftfeuchte received update
WoZiKlima.postUpdate(WoZi_Temperatur.state.toString + " / " + WoZi_Luftfeuchte.state.toString)

Text item=WoZiKlima icon=“sofa” label=“Wohnzimmer” // valuecolor=[>30=“red”,>25=“orange”,>15=“green”,<=15=“blue”]

How about using the search function of this forum like this.

Btw, I don’t think that the value color works on this string item.

Because i didn’t use the expression “formatting”.
And yes, that is the reason for the “//” in the line.

Thanks anyway.