bash for while until three methods usages

The first method : #! /bin/bash

declare -i sum=0 for i in {1..100};do let sum=$[$sum+$i] done echo "The total sum is $sum"

The second method: declare -i sum=0 declare -i i=0 while [ $i -le 100 ];do let sum=$[$sum+$i] let i++ done echo "The total sum is $sum"

The Thrid method: declare -i sum=0 declare -i i=0 until [ $i -gt 100 ];do let sum=$[$sum+$i] let i++ done echo "The Total sum is $sum"