新手，一个简单的计算，为什么结果是异常的

新手求助，一个简单的计算，为什么结果是错误的？
Dim a1 As Integer
Dim a2 As Single
Dim a3 As Single
Dim a4 As Single
Dim a5 As Single

Dim sum As Double


a1 = 8860
a2 = 1.145
a3 = 0.965
a4 = 1.13
a5 = 6025.3

sum = a1 * a2 * a3 * a4 * a5

Text1 = a1 & "×" & a2 & "×" & a3 & "×" & a4 & "×" & a5 & "=" & sum


计算结果为8860×1.145×0.965×1.13×6025.3=66653599.2156601
为什么不是66653604.5793(计算器计算的结果)

[解决办法]
数据类型使用的精度不够，看看这个。和计算器一致：

VB code

Option ExplicitPrivate Sub Form_Load()    Dim a1 As Double    Dim a2 As Double    Dim a3 As Double    Dim a4 As Double    Dim a5 As Double        Dim sum As Double            a1 = 8860#    a2 = 1.145    a3 = 0.965    a4 = 1.13    a5 = 6025.3        sum = a1 * a2 * a3 * a4 * a5        Text1 = a1 & "¡Á" & a2 & "¡Á" & a3 & "¡Á" & a4 & "¡Á" & a5 & "=" & sum    Me.Caption = "66653604.5793"End Sub