diff --git a/.gitignore b/.gitignore
deleted file mode 100644
index 7b065ff5fc..0000000000
--- a/.gitignore
+++ /dev/null
@@ -1,19 +0,0 @@
-# If you need to exclude files such as those generated by an IDE, use
-# $GIT_DIR/info/exclude or the core.excludesFile configuration variable as
-# described in https://git-scm.com/docs/gitignore
-
-*.egg-info
-*.pot
-*.py[co]
-.tox/
-__pycache__
-MANIFEST
-dist/
-docs/_build/
-docs/locale/
-node_modules/
-tests/coverage_html/
-tests/.coverage*
-build/
-tests/report/
-tests/screenshots/
diff --git a/django/db/models/expressions.py b/django/db/models/expressions.py
index 667e9f93c6..385803c137 100644
--- a/django/db/models/expressions.py
+++ b/django/db/models/expressions.py
@@ -61,6 +61,13 @@ class Combinable:
     BITXOR = "#"
 
     def _combine(self, other, connector, reversed):
+        if connector in [self.DIV, self.MUL, self.ADD, self.SUB] and isinstance(
+            other, (int, float, Decimal)
+        ):
+            other = Value(
+                Decimal(str(other)),
+                output_field=fields.DecimalField(max_digits=20, decimal_places=10),
+            )
         if not hasattr(other, "resolve_expression"):
             # everything must be resolvable to an expression
             other = Value(other)
@@ -1172,6 +1179,8 @@ class Value(SQLiteNumericMixin, Expression):
     def resolve_expression(
         self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False
     ):
+        if isinstance(self.value, Decimal) and not self.output_field:
+            self.output_field = fields.DecimalField(max_digits=20, decimal_places=10)
         c = super().resolve_expression(query, allow_joins, reuse, summarize, for_save)
         c.for_save = for_save
         return c