function calculator() {

	document.getElementById('calculator').style.display = 'block';

	document.getElementById('sqr_metres').style.display = 'none';

}



function calculate() {

	document.getElementById('calculator').style.display = 'none';

	document.getElementById('sqr_metres').style.display = 'block';

	var aside = document.getElementById('a_side').value;

	var bside = document.getElementById('b_side').value;

	

	var total = aside * bside;

	document.getElementById('sqr_metres').value = total;

}