diff --git a/ex-3_01-08.scm b/ex-3_01-08.scm
new file mode 100644
index 0000000..cc14dd7
--- /dev/null
+++ b/ex-3_01-08.scm
@@ -0,0 +1,151 @@
+(load "util.scm")
+
+(display "\nex-3.1 - accumulator\n")
+
+(define (make-accumulator value)
+  (define (accumulate new-value)
+    (set! value (+ value new-value))
+    value)
+  accumulate)
+
+(define A (make-accumulator 5))
+(assert (A 10) 15)
+(assert (A 10) 25)
+
+(display "\nex-3.2 - monitored calls\n")
+
+(define (make-monitored proc)
+  (define count 0)
+  (define (dispatch m)
+    (cond ((eq? m 'how-many-calls?) count)
+          ((eq? m 'reset-count) (set! count 0) count)
+          (else (set! count (inc count))
+                (proc m))))
+  dispatch)
+
+(define s (make-monitored sqrt))
+
+(assert (s 100) 10)
+(assert (s 9) 3)
+(assert (s 'how-many-calls?) 2)
+(s 'reset-count)
+(assert (s 'how-many-calls?) 0)
+
+
+(display "\nex-3.3 - account with password\n")
+
+(define (make-account balance password)
+  (define invalid-pw-attempts 0)
+  (define (withdraw amount)
+    (if (>= balance amount)
+        (begin (set! balance (- balance amount))
+               balance)
+        "Insufficient funds"))
+  (define (deposit amount)
+    (set! balance (+ balance amount))
+    balance)
+  (define (incorrect-password value)
+    "Incorrect password")
+  (define (call-the-cops value)
+    "Call the cops!")
+  (define (dispatch pw m)
+    (if (eq? pw password)
+      (begin
+        (set! invalid-pw-attempts 0)
+        (cond
+          ((eq? m 'withdraw) withdraw)
+          ((eq? m 'deposit) deposit)
+          (else (error "Unknown request -- MAKE-ACCOUNT" m))))
+      (cond
+         ((= invalid-pw-attempts 3) call-the-cops)
+         (else
+           (set! invalid-pw-attempts (inc invalid-pw-attempts))
+           incorrect-password))))
+  dispatch)
+
+(define acc (make-account 100 'secret-password))
+
+(assert ((acc 'secret-password 'withdraw) 40) 60)
+(assert ((acc 'some-other-password 'deposit) 50) "Incorrect password")
+
+(display "\nex-3.4 - call the cops\n")
+
+((acc 'some-other-password 'deposit) 50)
+(assert ((acc 'secret-password 'deposit) 50) 110)
+((acc 'some-other-password 'deposit) 50)
+((acc 'some-other-password 'deposit) 50)
+((acc 'some-other-password 'deposit) 50)
+(assert ((acc 'some-other-password 'deposit) 50) "Call the cops!")
+
+
+(display "\nex-3.5 - pi via integral\n")
+
+(define (rand) (random 65536))
+
+(define (estimate-pi trials)
+  (sqrt (/ 6 (monte-carlo trials cesaro-test))))
+(define (cesaro-test)
+   (= (gcd (rand) (rand)) 1))
+(define (monte-carlo trials experiment)
+  (define (iter trials-remaining trials-passed)
+    (cond ((= trials-remaining 0)
+           (/ trials-passed trials))
+          ((experiment)
+           (iter (- trials-remaining 1) (+ trials-passed 1)))
+          (else
+           (iter (- trials-remaining 1) trials-passed))))
+  (iter trials 0))
+
+(display (estimate-pi 1000)) (newline)
+
+(define (estimate-integral P x1 x2 y1 y2 trials)
+  (define (area-test)
+    (P (random-in-range x1 (inc x2))
+       (random-in-range y1 (inc y2))))
+  (let ((area-rectangle (* (abs (- x2 x1)) (abs (- y2 y1)))))
+    (* area-rectangle (monte-carlo trials area-test))))
+
+(define (p x y) (<= (+ (square (- x 50)) (square (- y 50)))
+                    (square 50)))
+
+; I had to use a bigger circle because random-in-range returns integers. If the
+; circle is too small the random coordinates lying within and without of the
+; circle are skewed.
+(let ((area-circle (estimate-integral p 0 100 0 100 1000))
+      (radius-circle 50.))
+  (let ((pi (/ area-circle (square radius-circle))))
+    (assert (< pi 3.4) #t)
+    (assert (> pi 3.0) #t)))
+
+(display "\nex-3.6 - rand\n")
+
+(define (make-rand)
+  (define x 0)
+  (define a 1664525)
+  (define c 1013904223)
+  (define m (expt 2 32))
+  (define (reset new-x)
+    (set! x new-x))
+  (define (generate)
+     (set! x (modulo (+ (* a x) c) m))
+     x)
+  (define (dispatch command)
+    (cond
+      ((eq? command 'reset) reset)
+      ((eq? command 'generate) (generate))
+      (else (error "Unknown request -- RAND" m))))
+  dispatch)
+
+(define rand (make-rand))
+(let ((r3 (rand 'generate))
+      (r2 (rand 'generate))
+      (r1 (rand 'generate)))
+  ((rand 'reset) 0)
+  (assert r1 (rand 'generate))
+  (assert r2 (rand 'generate))
+  (assert r3 (rand 'generate)))
+
+(display "\nex-3.7\n")
+
+(display "\nex-3.8\n")
+
diff --git a/ex-3_01-xx.scm b/ex-3_01-xx.scm
deleted file mode 100644
index ac5c349..0000000
--- a/ex-3_01-xx.scm
+++ /dev/null
@@ -1,82 +0,0 @@
-(load "util.scm")
-
-(display "\nex-3.1\n")
-
-(define (make-accumulator value)
-  (define (accumulate new-value)
-    (set! value (+ value new-value))
-    value)
-  accumulate)
-
-(define A (make-accumulator 5))
-(assert (A 10) 15)
-(assert (A 10) 25)
-
-(display "\nex-3.2\n")
-
-(define (make-monitored proc)
-  (define count 0)
-  (define (dispatch m)
-    (cond ((eq? m 'how-many-calls?) count)
-          ((eq? m 'reset-count) (set! count 0) count)
-          (else (set! count (inc count))
-                (proc m))))
-  dispatch)
-
-(define s (make-monitored sqrt))
-
-(assert (s 100) 10)
-(assert (s 9) 3)
-(assert (s 'how-many-calls?) 2)
-(s 'reset-count)
-(assert (s 'how-many-calls?) 0)
-
-
-(display "\nex-3.3\n")
-
-(define (make-account balance password)
-  (define invalid-pw-attempts 0)
-  (define (withdraw amount)
-    (if (>= balance amount)
-        (begin (set! balance (- balance amount))
-               balance)
-        "Insufficient funds"))
-  (define (deposit amount)
-    (set! balance (+ balance amount))
-    balance)
-  (define (incorrect-password value)
-    "Incorrect password")
-  (define (call-the-cops value)
-    "Call the cops!")
-  (define (dispatch pw m)
-    (if (eq? pw password)
-      (begin
-        (set! invalid-pw-attempts 0)
-        (cond
-          ((eq? m 'withdraw) withdraw)
-          ((eq? m 'deposit) deposit)
-          (else (error "Unknown request -- MAKE-ACCOUNT" m))))
-      (cond
-         ((= invalid-pw-attempts 3) call-the-cops)
-         (else
-           (set! invalid-pw-attempts (inc invalid-pw-attempts))
-           incorrect-password))))
-  dispatch)
-
-(define acc (make-account 100 'secret-password))
-
-(assert ((acc 'secret-password 'withdraw) 40) 60)
-(assert ((acc 'some-other-password 'deposit) 50) "Incorrect password")
-
-(display "\nex-3.4\n")
-
-((acc 'some-other-password 'deposit) 50)
-(assert ((acc 'secret-password 'deposit) 50) 110)
-((acc 'some-other-password 'deposit) 50)
-((acc 'some-other-password 'deposit) 50)
-((acc 'some-other-password 'deposit) 50)
-(assert ((acc 'some-other-password 'deposit) 50) "Call the cops!")
-
-
-(display "\nex-3.5\n")
-
diff --git a/ex-3_09-xx.scm b/ex-3_09-xx.scm
new file mode 100644
index 0000000..3c8f12e
--- /dev/null
+++ b/ex-3_09-xx.scm
@@ -0,0 +1,4 @@
+(load "util.scm")
+
+(display "\nex-3.9\n")
+
diff --git a/util.scm b/util.scm
index 4babb59..2400b1f 100644
--- a/util.scm
+++ b/util.scm
@@ -53,3 +53,9 @@
       (op (car sequence)
           (fold-right op initial (cdr sequence)))))
 
+; From exercise 3.5
+(define (random-in-range low high)
+  (let ((range (- high low)))
+    (+ low (random range))))
+
+'util-loaded