How many {child} are for {Conrad Hilton} ?
How many kids does Conrad Hilton have?
Conrad Hilton has how many children?
SELECT ( COUNT ( ?l ) AS ?n ) { resource:Conrad_Hilton property:child ?l }
SELECT (COUNT(?obj) AS ?objs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q324956> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P40> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
} 

SELECT (COUNT(?obj) AS ?value ) { wd:Q324956 wdt:P40 ?obj }
4