VB程序设计题：由输入对话框输入n（n必须为大于零且小于30的自然数），

Question

计算表达式sum=1/2+1/6+…+1/(k*(k+1))的值，（k<n）

Answer 1

Private sub form_click()

Dim n as integer, sum as double, k as integer

N = val(inputbox(“n=”,”请输入自然数n（n>0且n<30）”))

Do while n <= 0 !! or !! n > 30

N = val(inputbox(“n=”,”请重新输入”))

Loop

Sum = 0

K = 0

Do

K = !! k+1 !!

Sum = sum + 1/(k * (k+1))

Loop until !! (k+1) > n !!

Label1.caption = “sum” + str(sum)

End sub

Answer 2

private
sub
form_click()
dim
n
as
integer,
i
as
integer,
y
as
single,
zh
as
single
n
=
inputbox("请输入n",
"n是大于0小于30的整数")
i
=
1
'此行以下4行已经修改
while
i
<=
n
zh
=
1
/
(i
*
(i
+
1))
i
=
i
+
1
y
=
y
+
zh
wend
print
y
end
sub