diff --git a/chapter2.lisp b/chapter2.lisp
index f2bc972..b1cf998 100644
--- a/chapter2.lisp
+++ b/chapter2.lisp
@@ -97,3 +97,11 @@ and upper bound."
   (/ (- (upper-bound x) (lower-bound x))
      2.0))
 
+;; Exercise 2.10
+(defun div-interval (a b)
+  (if (zerop (width-interval b))
+      (error "Cannot divide by 0 width interval")
+   (mul-interval
+    a
+    (make-interval (/ 1.0 (upper-bound b))
+		   (/ 1.0 (lower-bound b))))))