diff --git a/ProjectEuler/Problem15.java b/ProjectEuler/Problem15.java
new file mode 100644
index 000000000000..2cc3c608da1d
--- /dev/null
+++ b/ProjectEuler/Problem15.java
@@ -0,0 +1,18 @@
+package ProjectEuler;
+
+public class Problem15 {
+  public static void main(String[] args) {
+    assert solution() == 137846528820L;
+  }
+
+  public static long solution() {
+    long paths = 1;
+
+    for (int i = 0; i < 20; i++) {
+      paths *= (2 * 20) - i;
+      paths /= i + 1;
+    }
+
+    return paths;
+  }
+}
diff --git a/ProjectEuler/Problem19.java b/ProjectEuler/Problem19.java
new file mode 100644
index 000000000000..0dab323a9029
--- /dev/null
+++ b/ProjectEuler/Problem19.java
@@ -0,0 +1,46 @@
+package ProjectEuler;
+
+import java.util.Arrays;
+
+public class Problem19 {
+  public static void main(String[] args) {
+    assert solution() == 171;
+  }
+
+  public static int solution() {
+    int year = 1901;
+    boolean leapYear = false;
+    int totalSundays = 0;
+    int currentDay = 2; // start on a monday
+
+    while (year <= 2000) {
+      leapYear = false;
+      if (year % 4 == 0) {
+        if (year % 100 == 0 && year % 400 == 0) {
+          leapYear = true;
+        } else leapYear = year % 100 != 0 || year % 400 == 0;
+      }
+
+      for (int month = 1; month <= 12; month++) {
+        if (currentDay == 7) {
+          totalSundays++;
+        }
+        if (Arrays.asList(1, 3, 5, 7, 8, 10, 12).contains(month)) {
+          currentDay += 3;
+        } else if (Arrays.asList(4, 6, 9, 11).contains(month)) {
+          currentDay += 2;
+        } else if (leapYear) {
+          currentDay += 1;
+        }
+
+        if (currentDay > 7) {
+          currentDay -= 7;
+        }
+      }
+
+      year++;
+    }
+
+    return totalSundays;
+  }
+}
diff --git a/ProjectEuler/Problem26.java b/ProjectEuler/Problem26.java
new file mode 100644
index 000000000000..3e62bc8376f6
--- /dev/null
+++ b/ProjectEuler/Problem26.java
@@ -0,0 +1,36 @@
+package ProjectEuler;
+
+public class Problem26 {
+
+  public static void main(String[] args) {
+    assert solution() == 983;
+  }
+
+  public static int solution() {
+    int sequenceSize = 0;
+    int d = 0;
+
+    for (int i = 1000; i > 1; i--) {
+      if (sequenceSize >= i) {
+        break;
+      }
+
+      int[] remaindersArray = new int[i];
+      int val = 1;
+      int pos = 0;
+
+      while (remaindersArray[val] == 0 && val != 0) {
+        remaindersArray[val] = pos;
+        val *= 10;
+        val %= i;
+        pos++;
+      }
+
+      if (pos - remaindersArray[val] > sequenceSize) {
+        d = i;
+        sequenceSize = pos - remaindersArray[val];
+      }
+    }
+    return d;
+  }
+}
diff --git a/ProjectEuler/Problem31.java b/ProjectEuler/Problem31.java
new file mode 100644
index 000000000000..8efef70222b3
--- /dev/null
+++ b/ProjectEuler/Problem31.java
@@ -0,0 +1,36 @@
+package ProjectEuler;
+
+/**
+ * In the United Kingdom the currency is made up of pound (£) and pence (p). There are eight coins
+ * in general circulation:
+ *
+ * <p>1p, 2p, 5p, 10p, 20p, 50p, £1 (100p), and £2 (200p).
+ *
+ * <p>It is possible to make £2 in the following way:
+ *
+ * <p>1×£1 + 1×50p + 2×20p + 1×5p + 1×2p + 3×1p
+ *
+ * <p>How many different ways can £2 be made using any number of coins?
+ *
+ * <p>link: https://projecteuler.net/problem=31
+ */
+public class Problem31 {
+  public static void main(String[] args) {
+    assert solution() == 73682;
+  }
+
+  public static int solution() {
+    int target = 200;
+    int[] coins = {1, 2, 5, 10, 20, 50, 100, 200};
+    int[] combos = new int[201];
+    combos[0] = 1;
+
+    for (int coin : coins) {
+      for (int i = coin; i <= target; i++) {
+        combos[i] += combos[i - coin];
+      }
+    }
+
+    return combos[200];
+  }
+}