Step 7: Add Multiplication and Division Problems

In the seventh part of this tutorial, you'll add multiplication and division problems, but first think about how to make that change. Consider the initial step, which involves storing values.

To add multiplication and division problems

  1. Add four more integer variables to the form.

    Public Class Form1
    
        ' Create a Random object called randomizer  
        ' to generate random numbers. 
        Private randomizer As New Random
    
        ' These integer variables store the numbers  
        ' for the addition problem.  
        Private addend1 As Integer 
        Private addend2 As Integer 
    
    
        ' These integer variables store the numbers  
        ' for the subtraction problem.  
        Private minuend As Integer 
        Private subtrahend As Integer 
    
        ' These integer variables store the numbers  
        ' for the multiplication problem.  
        Private multiplicand As Integer 
        Private multiplier As Integer 
    
        ' These integer variables store the numbers  
        ' for the division problem.  
        Private dividend As Integer 
        Private divisor As Integer 
    
        ' This integer variable keeps track of the  
        ' remaining time. 
        Private timeLeft As Integer
    
  2. As you did before, modify the StartTheQuiz() method to fill in random numbers for the multiplication and division problems.

    ''' <summary> 
    ''' Start the quiz by filling in all of the problem  
    ''' values and starting the timer.  
    ''' </summary> 
    ''' <remarks></remarks> 
    Public Sub StartTheQuiz()
    
        ' Fill in the addition problem. 
        ' Generate two random numbers to add. 
        ' Store the values in the variables 'addend1' and 'addend2'.
        addend1 = randomizer.Next(51)
        addend2 = randomizer.Next(51)
    
        ' Convert the two randomly generated numbers 
        ' into strings so that they can be displayed 
        ' in the label controls.
        plusLeftLabel.Text = addend1.ToString()
        plusRightLabel.Text = addend2.ToString()
    
        ' 'sum' is the name of the NumericUpDown control. 
        ' This step makes sure its value is zero before 
        ' adding any values to it.
        sum.Value = 0
    
        ' Fill in the subtraction problem.
        minuend = randomizer.Next(1, 101)
        subtrahend = randomizer.Next(1, minuend)
        minusLeftLabel.Text = minuend.ToString()
        minusRightLabel.Text = subtrahend.ToString()
        difference.Value = 0
    
        ' Fill in the multiplication problem.
        multiplicand = randomizer.Next(2, 11)
        multiplier = randomizer.Next(2, 11)
        timesLeftLabel.Text = multiplicand.ToString()
        timesRightLabel.Text = multiplier.ToString()
        product.Value = 0
    
        ' Fill in the division problem.
        divisor = randomizer.Next(2, 11)
        Dim temporaryQuotient As Integer = randomizer.Next(2, 11)
        dividend = divisor * temporaryQuotient
        dividedLeftLabel.Text = dividend.ToString()
        dividedRightLabel.Text = divisor.ToString()
        quotient.Value = 0
    
        ' Start the timer.
        timeLeft = 30
        timeLabel.Text = "30 seconds"
        Timer1.Start()
    
    End Sub
    
  3. Modify the CheckTheAnswer() method so that it also checks the multiplication and division problems.

    ''' <summary> 
    ''' Check the answers to see if the user got everything right. 
    ''' </summary> 
    ''' <returns>True if the answer's correct, false otherwise.</returns> 
    ''' <remarks></remarks> 
    Public Function CheckTheAnswer() As Boolean 
    
        If addend1 + addend2 = sum.Value AndAlso 
           minuend - subtrahend = difference.Value AndAlso 
           multiplicand * multiplier = product.Value AndAlso 
           dividend / divisor = quotient.Value Then 
    
            Return True 
        Else 
            Return False 
        End If 
    
    End Function
    

    You can't easily enter the multiplication sign (×) and the division sign (÷) using the keyboard, so Visual C# and Visual Basic accept an asterisk (*) for multiplication and a slash mark (/) for division.

  4. Change the last part of the timer's Tick event handler so that it fills in the correct answer when time runs out.

    Else 
        ' If the user ran out of time, stop the timer, show 
        ' a MessageBox, and fill in the answers.
        Timer1.Stop()
        timeLabel.Text = "Time's up!"
        MessageBox.Show("You didn't finish in time.", "Sorry!")
        sum.Value = addend1 + addend2
        difference.Value = minuend - subtrahend
        product.Value = multiplicand * multiplier
        quotient.Value = dividend / divisor
        startButton.Enabled = True 
    End If
    
  5. Save and run your program.

    Quiz takers must answer four problems to complete the quiz, as the following illustration shows.

    Math quiz with four problems

    Math quiz with four problems

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