what is the {proportion} for {potassium-40} has {decays to} as {argon-40} ?
What is the amount of potassium-40 before it decays into argon-40?
What is the proportion for potassium-40 before it decays to argon-40?
SELECT ?p WHERE { ?b property:proportion ?p . resource:potassium-40 property:decays_to ?b . ?b property:decays_to resource:argon-40 }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q2251076> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P816> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q1929004> .
?statement <http://www.wikidata.org/entity/P1107> ?value. 
} 

SELECT ?value WHERE { wd:Q2251076 p:P816 ?s . ?s ps:P816 wd:Q1929004 . ?s pq:P1107 ?value}