Quiz.py is returning the wrong number of correct answers. I have scoured my code and cannot find the issue.

import datetime
import random

from questions import Add, Multiply, Subtract


class Quiz:
    questions = []
    answers = []

    def __init__(self):
        question_types = (Add, Multiply)
        #generate 10 random questions with numbers from 1 to 10
        for _ in range(10):
            num1 = random.randint(1, 10)
            num2 = random.randint(1, 10)
            question = random.choice(question_types)(num1, num2)
            #add these questions into self.questions
            self.questions.append(question)

    def take_quiz(self):
        #log the start time
        self.start_time = datetime.datetime.now()

        #ask all of the questions
        for question in self.questions:
            #log if they got the question right
            self.answers.append(self.ask(question))
        else:
            #log the end time
            self.end_time = datetime.datetime.now()

        #show a sumary
        return self.summary()


    def ask(self, question):
        correct = False
        # log the start time
        question_start = datetime.datetime.now()

        # capture the answer
        answer = input(question.text + ' = ')

        # check the answer
        if answer == str(question.answer):
            correct = True

        # log the end time
        question_end = datetime.datetime.now()

        # if the anwer is right, send back true

        # otherwise send back false
        # send back the elapsed time
        return correct, question_end - question_start

    def total_correct(self):
        # return total # of correct answers
        total = 0
        for answer in self.answers:
            if answer [0]:
                total += 1
        return total

    def summary(self):
        # print how many you got right and total # of questions. 5/10
        print("You got {} out of {} right.".format(
                self.total_correct(), len(self.questions)
        ))
        print("it took you  {} seconds total.".format(
                (self.end_time-self.start_time).seconds
        ))


Quiz().take_quiz()