Install the latest Ansible version 2.9.2
How to use without id_rsa.pub , authorized_keys 🙈

Test environment

Ubuntu 18.04
Ansible 2.9.2

Install

$ apt-get update
$ apt-get install software-properties-common
$ apt-add-repository --yes --update ppa:ansible/ansible
$ apt-get install ansible

$ ansible --version
ansible 2.9.2
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/dist-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.17 (default, Nov  7 2019, 10:07:09) [GCC 7.4.0]

Modify Ansible Configuration File

Modify both /etc/ansible/ansible.cfg and /etc/ansible/hosts Ref Link

$ vi /etc/ansible/ansible.cfg

[defaults]
host_key_checking = False
[ssh_connection]
ssh_args = -C -o ControlMaster=auto -o ControlPersist=60s
control_path = /dev/shm/cp%%h-%%p-%%r

$ vi /etc/ansible/hosts

[child]
182.252.133.71
182.252.133.72

[child:vars]
ansible_user=root
ansible_password=Password1!

Run

Check the operation with the default ping command of ad-hoc.
Once ping and pong are confirmed, you're done! 👌

$ ansible child -m ping -i /etc/ansible/hosts

182.252.133.72 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    },
    "changed": false,
    "ping": "pong"
}
182.252.133.71 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    },
    "changed": false,
    "ping": "pong"
}