how to put the loop valuable in a json body on unix command?

Question

In Linux, I am trying to do something on command as:

for i in {1..10}
do  
    let i=i*10 
    curl -X POST http://server/MyApiCall -d'{"x": $i, "y": 0}' 
done

Currently it does not work, as "$i" is not valid in this json body. Does anyone the correct format for that ?

Thanks.