diff --git a/Cargo.lock b/Cargo.lock
index d7215f8..919a337 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -65,3 +65,11 @@ version = "0.1.0"
 [[package]]
 name = "d08t2"
 version = "0.1.0"
+
+[[package]]
+name = "d09t1"
+version = "0.1.0"
+
+[[package]]
+name = "d09t2"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index 45a65eb..29a8e05 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,4 +18,6 @@ members = [
     "d07t2",
     "d08t1",
     "d08t2",
+    "d09t1",
+    "d09t2",
 ]
diff --git a/d09t1/Cargo.toml b/d09t1/Cargo.toml
new file mode 100644
index 0000000..c7a8ab6
--- /dev/null
+++ b/d09t1/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "d09t1"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/d09t1/demo_input.txt b/d09t1/demo_input.txt
new file mode 100644
index 0000000..70c5595
--- /dev/null
+++ b/d09t1/demo_input.txt
@@ -0,0 +1,3 @@
+0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45
\ No newline at end of file
diff --git a/d09t1/src/main.rs b/d09t1/src/main.rs
new file mode 100644
index 0000000..16d5190
--- /dev/null
+++ b/d09t1/src/main.rs
@@ -0,0 +1,50 @@
+use std::fs::read_to_string;
+
+fn main() {
+    let input = read_to_string("input.txt").unwrap();
+    println!("d09t1: {}", d09t1(&input));
+}
+
+pub fn d09t1(input: &str) -> isize {
+    input
+        .lines()
+        .map(str::split_whitespace)
+        .map(|line| {
+            line.map(str::parse::<isize>)
+                .map(Result::unwrap)
+                .collect::<Vec<_>>()
+        })
+        .map(find_next_in_sequence)
+        .sum()
+}
+
+pub fn find_next_in_sequence(sequence: Vec<isize>) -> isize {
+    let deltas = get_deltas(&sequence);
+    if *deltas.last().unwrap() == 0 {
+        *sequence.last().unwrap()
+    } else {
+        *sequence.last().unwrap() + find_next_in_sequence(deltas)
+    }
+}
+
+fn get_deltas(sequence: &Vec<isize>) -> Vec<isize> {
+    sequence
+        .windows(2)
+        .map(|window| window[1] - window[0])
+        .collect::<Vec<_>>()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_d09t1() {
+        let input = include_str!("../demo_input.txt");
+        assert_eq!(d09t1(input), 114);
+    }
+
+    #[test]
+    fn test_deltas() {
+        assert_eq!(get_deltas(&vec![0, 3, 6, 9, 12, 15]), vec![3, 3, 3, 3, 3])
+    }
+}
diff --git a/d09t2/Cargo.toml b/d09t2/Cargo.toml
new file mode 100644
index 0000000..34c9aba
--- /dev/null
+++ b/d09t2/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "d09t2"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/d09t2/demo_input.txt b/d09t2/demo_input.txt
new file mode 100644
index 0000000..70c5595
--- /dev/null
+++ b/d09t2/demo_input.txt
@@ -0,0 +1,3 @@
+0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45
\ No newline at end of file
diff --git a/d09t2/src/main.rs b/d09t2/src/main.rs
new file mode 100644
index 0000000..4fa7034
--- /dev/null
+++ b/d09t2/src/main.rs
@@ -0,0 +1,56 @@
+use std::fs::read_to_string;
+
+fn main() {
+    let input = read_to_string("input.txt").unwrap();
+    println!("d09t2: {}", d09t2(&input));
+}
+
+pub fn d09t2(input: &str) -> isize {
+    input
+        .lines()
+        .map(str::split_whitespace)
+        .map(|line| {
+            line.map(str::parse::<isize>)
+                .map(Result::unwrap)
+                .rev()
+                .collect::<Vec<_>>()
+        })
+        .map(find_next_in_sequence)
+        .sum()
+}
+
+pub fn find_next_in_sequence(sequence: Vec<isize>) -> isize {
+    let deltas = get_deltas(&sequence);
+    if deltas.iter().all(|&e| e == 0) {
+        *sequence.last().unwrap()
+    } else {
+        *sequence.last().unwrap() + find_next_in_sequence(deltas)
+    }
+}
+
+fn get_deltas(sequence: &Vec<isize>) -> Vec<isize> {
+    sequence
+        .windows(2)
+        .map(|window| window[1] - window[0])
+        .collect::<Vec<_>>()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_d09t2() {
+        let input = include_str!("../demo_input.txt");
+        assert_eq!(d09t2(input), 2);
+    }
+
+    #[test]
+    fn test_deltas() {
+        assert_eq!(get_deltas(&vec![0, 3, 6, 9, 12, 15]), vec![3, 3, 3, 3, 3])
+    }
+
+    #[test]
+    fn test_line_1() {
+        assert_eq!(d09t2("10 13 16 21 30 45"), 5)
+    }
+}