diff --git a/appendix-a.asciidoc b/appendix-a.asciidoc
index c411d26..bfbe7fb 100644
--- a/appendix-a.asciidoc
+++ b/appendix-a.asciidoc
@@ -186,7 +186,7 @@ The +geom.ex+ file is the same as in <<CH05-ET01,Étude 5-1>>.
 ==== +ask_area.ex+
 // [source,elixir]
 ----
-include::code/ch05-01/ask_area.ex[]
+include::code/ch05-02/ask_area.ex[]
 ----
 
 [[SOLUTION05-ET03]]
diff --git a/ch05-strings.asciidoc b/ch05-strings.asciidoc
index 7f33573..9572b6e 100644
--- a/ch05-strings.asciidoc
+++ b/ch05-strings.asciidoc
@@ -76,7 +76,7 @@ program work.
   This involves the following steps:
 
   * Use +String.strip/1+ to get rid of the trailing newline character
-  * Use +string_to_integer/1+ to convert the string to a number.
+  * Use +String.to_integer/1+ to convert the string to a number.
 
 +
 When you write the +-spec+ for this function (you _have_ been
@@ -123,7 +123,7 @@ Enter width > 3.5
     /bin/elixir/lib/iex/lib/iex/server.ex:19: IEx.Server.do_loop/1
 ----
 
-In this étude, you will use _regular expressions_ to make sure that input is numeric and to distinguish integers from floating point numbers. You need to do this because +binary_to_float/1+ will not accept a string like +"1812"+ as an argument. If you aren't familiar with regular expressions, there is a short summary in <<APPENDIXB>>.
+In this étude, you will use _regular expressions_ to make sure that input is numeric and to distinguish integers from floating point numbers. You need to do this because +String.to_float/1+ will not accept a string like +"1812"+ as an argument. If you aren't familiar with regular expressions, there is a short summary in <<APPENDIXB>>.
 
 The function you will use is the +Regex.match?/2+. It takes a regular expression pattern as its first argument and a string as its second argument. The function returns +true+ if the pattern matches the string, +false+ otherwise. Here are some examples in IEx.
 
diff --git a/code/ch05-01/ask_area.ex b/code/ch05-01/ask_area.ex
index 50c98fe..8bf1c1f 100644
--- a/code/ch05-01/ask_area.ex
+++ b/code/ch05-01/ask_area.ex
@@ -54,7 +54,7 @@ defmodule AskArea do
   
   def get_number(prompt) do
     input = IO.gets("Enter #{prompt} > ")
-    string_to_integer(String.strip(input))
+    String.to_integer(String.strip(input))
   end
   
   @doc """
diff --git a/code/ch05-02/ask_area.ex b/code/ch05-02/ask_area.ex
index 395dfb3..cb894bb 100644
--- a/code/ch05-02/ask_area.ex
+++ b/code/ch05-02/ask_area.ex
@@ -57,9 +57,9 @@ defmodule AskArea do
     input_str = String.strip(input)
     cond do
       Regex.match?(~r/^[+-]?\d+$/, input_str) ->
-        binary_to_integer(input_str)
+        String.to_integer(input_str)
       Regex.match?(~r/^[+-]?\d+\.\d+([eE][+-]?\d+)?$/, input_str) ->
-        binary_to_float(input_str)
+        String.to_float(input_str)
       true -> :error
     end
   end
diff --git a/code/ch05-03/dates.ex b/code/ch05-03/dates.ex
index 84d6709..9264546 100644
--- a/code/ch05-03/dates.ex
+++ b/code/ch05-03/dates.ex
@@ -15,7 +15,7 @@ defmodule Dates do
 
   def date_parts(date_str) do
     [y_str, m_str, d_str] = String.split(date_str, ~r/-/)
-    [binary_to_integer(y_str), binary_to_integer(m_str),
-      binary_to_integer(d_str)]
+    [String.to_integer(y_str), String.to_integer(m_str),
+      String.to_integer(d_str)]
   end
 end