+738 One day, River writes down the numbers 1,2,3,...999
What is the sum of all the digits that River wrote down?
thanks and please help :)
+166 Using the formula \(\frac{1}{2}(n)(n+1)\), we substitute the \(n\) as \(999\) to get \(\boxed{499500}\).
+37146 This is an arithemtic series with d = 1
S = (n/2) Γ (2a + (nβ1)d)
S = sum = 999/2 (2 + 998(1))
= 499500
+738 sorry, that's wrong too... thanks for taking the time to help though :)
+738 Just to clarify: the problem asks the sum of all the digits that he wrote down.
+738 thanks Guest! even though this isn't the answer, your explanation was the part I was stuck on! (I couldn't figure out how many 1s, 2s, 3s, etc. there were)
So the answer is 1+2+3...9 =45 *300 = 13500.\(\)
Sorry, I did have both of them but didn't read the question correctly:
(189, 300, 300, 300, 300, 300, 300, 300, 300, 300) >>>Total Number = 2889
(0, 300, 600, 900, 1200, 1500, 1800, 2100, 2400, 2700)>>Total Sum = 13500
