MongoDB update object in Array
'some test', so let's say you want to add 10 to 96 :

db.student.update({name:'student_1','courses.name':'Algebra'},{$inc:{"courses.$.grades.1":10}})


In the find part, you point to the courses with name 'Algebra'. The .$ points you to that found element. Of that found element, it will change the second (.1) value in the grades array. Using $, you don't need to know the position of the course in the array.