<p>Enter your £</p>
<p><input type="text" id="number"></p>
<button onclick="buttonClicked(document.getElementById('number').value)">Enter</button>

<div id="result"></div>

<script>

var result = document.getElementById('result');

function buttonClicked(number)
{
	result.innerHTML = '';
	result.innerHTML += 'There are ' + get50s(number) + ' fifty pence pieces in £' + number + '<br>';
	result.innerHTML += 'There are ' + get20s(number) + ' twenty pence pieces in £' + number + '<br>';
	result.innerHTML += 'There are ' + get10s(number) + ' ten pence pieces in £' + number + '<br>';
}
function get50s(number)
{
	return (number * 100) / 50;
}
function get20s(number)
{
	return (number * 100) / 20;
}
function get10s(number)
{
	return (number * 100) / 10;
}
</script>