Public Class Form3
    Dim phi As Decimal

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        phi = 22 / 7
        hsil.Text = (phi * (jari.Text * jari.Text * Tggi.Text)) / 3


    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        hsil.Text = ""
        jari.Text = ""
        Tggi.Text = ""
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Close()
    End Sub
End Class

untuk pembulatan angka di belakang koma code nya menyusul