diff --git a/src/combinations.rs b/src/combinations.rs
index e230119c1..06764cc85 100644
--- a/src/combinations.rs
+++ b/src/combinations.rs
@@ -208,8 +208,8 @@ fn remaining_for(n: usize, first: bool, indices: &[usize]) -> Option<usize> {
         indices
             .iter()
             .enumerate()
-            .fold(Some(0), |sum, (i, n0)| {
-                sum.and_then(|s| s.checked_add(checked_binomial(n - 1 - *n0, k - i)?))
+            .try_fold(0usize, |sum, (i, n0)| {
+                sum.checked_add(checked_binomial(n - 1 - *n0, k - i)?)
             })
     }
 }
diff --git a/src/combinations_with_replacement.rs b/src/combinations_with_replacement.rs
index 5d6a034b5..07c64c2c0 100644
--- a/src/combinations_with_replacement.rs
+++ b/src/combinations_with_replacement.rs
@@ -157,8 +157,8 @@ fn remaining_for(n: usize, first: bool, indices: &[usize]) -> Option<usize> {
         indices
             .iter()
             .enumerate()
-            .fold(Some(0), |sum, (i, n0)| {
-                sum.and_then(|s| s.checked_add(count(n - 1 - *n0, k - i)?))
+            .try_fold(0usize, |sum, (i, n0)| {
+                sum.checked_add(count(n - 1 - *n0, k - i)?)
             })
     }
 }
diff --git a/src/permutations.rs b/src/permutations.rs
index 21a84c401..cfdb06b2a 100644
--- a/src/permutations.rs
+++ b/src/permutations.rs
@@ -240,20 +240,16 @@ impl CompleteState {
                 if n < k {
                     return Some(0);
                 }
-                (n - k + 1..=n).fold(Some(1), |acc, i| {
-                    acc.and_then(|acc| acc.checked_mul(i))
-                })
+                (n - k + 1..=n).try_fold(1usize, |acc, i| acc.checked_mul(i))
             }
             CompleteState::Ongoing { ref indices, ref cycles } => {
-                let mut count: usize = 0;
-
-                for (i, &c) in cycles.iter().enumerate() {
-                    let radix = indices.len() - i;
-                    count = count.checked_mul(radix)
-                        .and_then(|count| count.checked_add(c))?;
-                }
-
-                Some(count)
+                cycles
+                    .iter()
+                    .enumerate()
+                    .try_fold(0usize, |acc, (i, &c)| {
+                        acc.checked_mul(indices.len() - i)
+                            .and_then(|count| count.checked_add(c))
+                    })
             }
         }
     }
diff --git a/src/powerset.rs b/src/powerset.rs
index f84cecfbd..9f0965bc5 100644
--- a/src/powerset.rs
+++ b/src/powerset.rs
@@ -82,7 +82,7 @@ impl<I> FusedIterator for Powerset<I>
 {}
 
 fn remaining_for(n: usize, k: usize) -> Option<usize> {
-    (k + 1..=n).fold(Some(0), |sum, i| {
-        sum.and_then(|s| s.checked_add(checked_binomial(n, i)?))
+    (k + 1..=n).try_fold(0usize, |sum, i| {
+        sum.checked_add(checked_binomial(n, i)?)
     })
 }