VBA - Find sum of 31st - 50th even numbers

[Robinhoods]

This is my homework : find sum of 31st - 50th even numbers between 1-100 by using either do-while or do-until loop. Pls help me

 

[Rick Rothstein]

While you cannot use this because it does not comply with your instructor's requirements to use a loop, you might find it interesting to know you do not need a loop at all. Beside encoding Gauss's formula that BSALV posted, you could also do this...

Sum31stTo50thEven = Application.Sum(Application.Index([ROW(1:100)], [2*ROW(31:50)]))

 

[Robinhoods]

... and neither of these is correct.

Sub Sum31stto50thEvenNumbers()
Dim loop_ctr As Integer
Dim even_number_counter As Integer
Dim sum As Integer

loop_ctr = 1
sum = 0

Do Until loop_ctr > 100
If (loop_ctr Mod 2 = 0) Then
even_number_counter = even_number_counter + 1
If (even_number_counter > 30 And even_number_counter <= 50) Then
sum = sum + loop_ctr
End If
End If

If (even_number_counter = 50) Then
Exit Do
End If

loop_ctr = loop_ctr + 1
Loop

MsgBox "Sum of 31st to 50th even numbers is : " & sum
End Sub
Is this correct?

 

[bebo021999]

Result is 1620:

Sub sumeven()
Dim loop_ctr&, even_ctr&, sum&
    Do
        even_ctr = loop_ctr * 2 + 31 * 2 ' start from 62 to 64,66,...
        sum = sum + even_ctr ' running sum
        loop_ctr = loop_ctr + 1
    Loop Until even_ctr >= 100
MsgBox "Sum of even number is: " & sum
End Sub

 

[StephenCrump]

Is this correct?

You tell me. Your code gives the answer 1,620. Is that the answer you expect?

From a presentation point of view, it's good practice to indent your code, e.g. as @bebo021999 has done. It makes your code easier to read, and easier to debug.

Sub Sum31stto50thEvenNumbers()

    Dim loop_ctr As Integer
    Dim even_number_counter As Integer
    Dim sum As Integer
   
    loop_ctr = 1
    sum = 0
   
    Do Until loop_ctr > 100
        If (loop_ctr Mod 2 = 0) Then
            even_number_counter = even_number_counter + 1
            If (even_number_counter > 30 And even_number_counter <= 50) Then
                sum = sum + loop_ctr
            End If
        End If
       
        If (even_number_counter = 50) Then
            Exit Do
        End If
       
        loop_ctr = loop_ctr + 1
    Loop
   
    MsgBox "Sum of 31st to 50th even numbers is : " & sum
End Sub

 

[Dave Patton]

Is the correct answer 410?
That would be the positive numbers > 30 and <=50.

formulas not VBA but the formula may help.

ser is a named array of numbers 1 to 100

T202203a.xlsm
	E	F	G	H	I
7	410
8	410		410	410	410
2c

Cell Formulas
Range	Formula
E7	E7	=50/2*(50/2+1)-30/2*(30/2+1)
E8	E8	=25*(25+1)-15*(15+1)
G8	G8	=SUM(IF((Ser>30)*(Ser<51)*(MOD(Ser,2)=0),Ser))
H8	H8	=SUM(IF(MOD(ROW(INDIRECT(B1&":"&C1)),2)=0,ROW(INDIRECT(B1&":"&C1))))
I8	I8	=SUM(IF(MOD(ROW(INDIRECT(31&":"&50)),2)=0,ROW(INDIRECT(31&":"&50))))

 

[Dave Patton]

Ignore the above post. I went back to delete the formulas etc but didn't complete the edits in time. It is quite late.



The original poster can confirm which result the he requires. Is it 1620 or 410?

 

[BSALV]

The sum of the positive numbers > 30 to 100 is 1620.

gaus says 100*101/2 -30*31/2 = 5050-465 = 4585
gaus also says that the sum of all the numbers between 31 and 50 = 50*51/2 - 30*31/2.
Like i read the question, the sum of the 31st until the 50st even number = that formula * 2, like i said yesterday.

 

[bebo021999]

@BSALV
Its his homework to practice Do Loop, not a formula option.

 

[BSALV]

for the loop-practice, see my answer #4