 All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars  perplexus dot info  2nd grade math (Posted on 2017-01-12) My son is doing a math worksheet. He is practicing the concept of 'carrying' when doing sums. The sheet has 16 problems, each is summing two three-digit numbers. What struck me as interesting was that the creator of the problems made every problem have at least two carries and most have three.

What is the probability distribution for the number of carries in finding the sum of two randomly selected three-digit numbers?

Feel free to generalize.

 No Solution Yet Submitted by Jer No Rating Comments: ( Back to comment list | You must be logged in to post comments.) re: solution -- simulation verification | Comment 2 of 4 | (In reply to solution by Charlie)

DefDbl A-Z
Dim crlf\$, ct(3)

Form1.Visible = True

Text1.Text = ""
crlf = Chr\$(13) + Chr\$(10)

mxtr = 1000000
For tr = 1 To mxtr
DoEvents
r1 = Int(Rnd(1) * 900) + 100
r2 = Int(Rnd(1) * 900) + 100
a1\$ = LTrim(Str(r1))
a2\$ = LTrim(Str(r2))
carryCt = 0: carry = 0
For p = 3 To 1 Step -1
d1 = Val(Mid(a1, p, 1))
d2 = Val(Mid(a2, p, 1))
s = d1 + d2 + carry
If s > 9 Then carry = 1: carryCt = carryCt + 1 Else carry = 0
Next
ct(carryCt) = ct(carryCt) + 1
Next tr

For c = 0 To 3
Text1.Text = Text1.Text & Str(ct(c))
Next
Text1.Text = Text1.Text & crlf

Text1.Text = Text1.Text & crlf & " done"

End Sub

produces

134550 342975 360366 162109

for counts of 0, 1, 2 or 3 carries adding two 3-digit numbers.

 Posted by Charlie on 2017-01-12 21:38:09 Please log in:

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