var alt_table='';
function open_menu_table(id) {	
	var i=0;

	if(alt_table!=id) {	
		if(alt_table) {	
			open_menu_table(alt_table);
		}
	} else {	
		alt_table='';
	}
	
	while(i<=alt_table) {
if (document.getElementById(id).style.display == 'none') {	
document.getElementById(id).style.display = 'inline';
alt_table=id;
} else {	
document.getElementById(id).style.display = 'none';
}
i++;
	}
}

function randomMath(){
	//alert("randomMath()");

	var mina = 0;
	var maxa = 8;
	var maxb =1;
	var zahl1 = new Array(1,2,3,4,5,6,7,8,9);	
	var zahl2 = new Array(1,2,3,4,5,6,7,8,9);
	var rechne = new Array("+","-");
	var info_string = "";
	var r1 = mina + parseInt( Math.random() * ( maxa-mina+1 ));
	mina = 0;
	var r2 = mina + parseInt( Math.random() * ( maxa-mina+1 ));
	mina = 0;
	var r3 = mina + parseInt( Math.random() * ( maxb-mina+1 ));
	mina = 0;
	
	if(r1 < r2){
		r3 = 0;	
	}
	
	info_string = info_string + "Berechne " + zahl1[r1]+" " +rechne[r3]+" " + zahl2[r2];
	//alert(info_string);
	document.getElementById('rechnen').innerHTML = info_string;
	document.getElementById('a').value = zahl1[r1];
	document.getElementById('b').value = zahl2[r2];
	document.getElementById('rstring').value = "\"" + rechne[r3]+"\"";
}