I had this code in my snippet bucket. Change as needed.
var elements = document.getElementsByClassName('hidden');
var randomElement = elements[Math.floor(Math.random() * elements.length)];
randomElement.style.display = 'block';
Thanks for your response i ended up finding this which worked for me. I will have a play around with your thanks
var elems = $(".t1");
if (elems.length) {
var keep = Math.floor(Math.random() * elems.length);
for (var i = 0; i < elems.length; ++i) {
if (i !== keep) {
$(elems[i]).hide();
}
}