Why my vb calculation appears infinity?

Question

The calcluator is set to calculate current, resistance and power.
the followings are the code for the calculator:
Public Class Form3
Dim Black As Integer = 0
Dim Brown As Integer = 1
Dim Red As Integer = 2
Dim Orange As Integer = 3
Dim Yellow As Integer = 4
Dim Green As Integer = 5
Dim Blue As Integer = 6
Dim Violet As Integer = 7
Dim Gray As Integer = 8
Dim White As Integer = 9
Dim Gold As Integer = 5
Dim Silver As Integer = 10
Dim None As Integer = 20
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Private Sub dud1_SelectedItemChanged(sender As Object, e As EventArgs) Handles dud1.SelectedItemChanged
If dud1.SelectedItem = "Black" Then
txt7.BackColor = Color.Black
txt7.Text = Black
ElseIf dud1.SelectedItem = "Brown" Then
txt7.BackColor = Color.Brown
txt7.Text = Brown
ElseIf dud1.SelectedItem = "Red" Then
txt7.BackColor = Color.Red
txt7.Text = Red
ElseIf dud1.SelectedItem = "Orange" Then
txt7.BackColor = Color.Orange
txt7.Text = Orange
ElseIf dud1.SelectedItem = "Yellow" Then
txt7.BackColor = Color.Yellow
txt7.Text = Yellow
ElseIf dud1.SelectedItem = "Green" Then
txt7.BackColor = Color.Green
txt7.Text = Green
ElseIf dud1.SelectedItem = "Blue" Then
txt7.BackColor = Color.Blue
txt7.Text = Blue
ElseIf dud1.SelectedItem = "Violet" Then
txt7.BackColor = Color.Violet
txt7.Text = Violet
ElseIf dud1.SelectedItem = "Gray" Then
txt7.BackColor = Color.Gray
txt7.Text = Gray
ElseIf dud1.SelectedItem = "White" Then
txt7.BackColor = Color.White
txt7.Text = White
End If
End Sub
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Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
txt1.Text = Val(txt7.Text + txt8.Text) * 10 ^ (Val(txt9.Text))
txt2.Text = (Val(txt7.Text + txt8.Text) * 10 ^ (Val(txt9.Text))) * Val(Val(txt10.Text) / 100)
End Sub

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
txt6.Text = Val(txt5.Text) / Val(txt12.Text)
txt11.Text = Val(txt5.Text) * Val(txt6.Text)
txt12.Text = Val(1 / (Val(1 / (txt3.Text)) + Val(1 / txt4.Text)))
End Sub
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The calculation appears "infinity" for current when press "calculate" for the first time. After pressing it for second time then the actual no. appear.
If I change the no. of voltage then press calculate, it will show the previous no. The actual no. appears only when the "calculate" button pressed twice.
What's the problem?

Answer 1

Looks like you have some unintialized variables. Dividing by txt12 before giving it a value will use its default value of zero.

Answer 2

Bug solved. Thank you. ^^