different ways of summing lists of numbers

gistfile1.rkt

#lang racket

(define (my-sum-1 lst)
  (cond
    ((null? lst) 0)
    (else (+ (car lst) (my-sum-1 (cdr lst))))))

(define (my-sum-2 lst)
  (define (my-sum-iter res lst)
    (cond
      ((null? lst) res)
      (else (my-sum-iter (+ (car lst) res) (cdr lst)))))
  (my-sum-iter 0 lst))

(define (my-sum-3 lst)
  (apply + lst))

(define (my-range start end)
  (cond
    ((= start end) '())
    (else (cons start (my-range (+ 1 start) end)))))