db={"restaurants":[{"_id":ObjectId("625c95836be34e3c73c37316"),"cuisine":"Chinese","grades":[{"date":ISODate("2014-02-25T00:00:00Z"),"grade":"A","score":112},{"date":ISODate("2013-08-14T00:00:00Z"),"grade":"C","score":28},{"date":ISODate("2012-07-18T00:00:00Z"),"grade":"A","score":13},{"date":ISODate("2012-03-09T00:00:00Z"),"grade":"A","score":13},{"date":ISODate("2011-10-27T00:00:00Z"),"grade":"A","score":12},{"date":ISODate("2011-05-19T00:00:00Z"),"grade":"A","score":13}],"name":"janette"},{"_id":ObjectId("625c95836be34e3c73c37317"),"cuisine":"Chinese","grades":[{"date":ISODate("2014-01-07T00:00:00Z"),"grade":"A","score":17},{"date":ISODate("2013-05-09T00:00:00Z"),"grade":"B","score":107}],"name":"Annie'S Kitchen"}]}

db.restaurants.aggregate([{"$match":{$expr:{"$allElementsTrue":{"$map":{"input":"$grades","as":"g","in":{$and:[{$gt:["$$g.score",80]},{$lt:["$$g.score",100]}]}}}}}}])