Question

let \[a★b = ab + a + b\]So,How many consecutive nines are there at the end of :
\[1★(2★(3 ★(4★...(99★100))))\]

Answer 1

it is equal to factorial 100

Answer 2

6*4

Answer 3

6 zeros in 25!

Answer 4

i think there is a zero counting theorem though ...

Answer 5

yep

Answer 6

it seems that i have forgotten it though

Answer 7

its 24 i think

Answer 8

\[\lfloor \frac{101}{5} \rfloor+\lfloor \frac{101}{25} \rfloor=24\]

Answer 9

it is 24 ... i checked from WA.
yep ... that's the one ...