(* 3.1 *) 
 
(25 * 850) + (28 * 850) + (31 * 850) ;; 
(25 + 28 + 31) * 850 ;; 
 
(* 3.2 *) 
 
let pi = 3.1415 ;; 
pi ;; 
2.0 *. pi ;; 
let jikyu = 850 ;; 
(25 * jikyu) + (28 * jikyu) + (31 * jikyu) ;; 
 
(* 3.3 *) 
 
(* 3.4 *)