var problems = [{question:'1+1',options:['0','1','2'],answer:'2'},
  {question:'12-3',options:['12','9','6'],answer:'9'},
  {question:'5*6',options:['15','18','30'],answer:'30'},
  {question:'124/4',options:['31','62','124'],answer:'31'},
  {question:'15*5',options:['155','75','65'],answer:'75'},
  {question:'183+37',options:['210','220','230'],answer:'220'}];
var n = 0; // The current problem number
var correct = 0;

// Function to display the current problem.
function displayProblem() {
  $('#question').text(problems[n].question);
  $('#one').text(problems[n].options[0]);
  $('#two').text(problems[n].options[1]);
  $('#three').text(problems[n].options[2]);
}

// Clicking one of the answer buttons calls this function.
function answer() {
  if($(this).text() == problems[n].answer)
    correct = correct+1;
  if(n < 5) {
    n = n + 1;
    displayProblem();
  } else {
    $('#questions').hide();
    $('#score').text(correct);
    $('#results').show();
  }
}

function setUp() {
  $('#one').click(answer);
  $('#two').click(answer);
  $('#three').click(answer);
  displayProblem();
  $('#results').hide();
}

$(document).ready(setUp);