[Lonesome in Massachussets]

Another interesting, but less useful trick than the rule of 11. (How offen do you need to multiply by 11 anyway?)

What’s the square root of:

12345678987654321 ?

Hint: It was instantly obvious to me the first time I saw it.

[Lonesome in Massachussets]

How many trailing zeros in 40000005!

40000005! = 40000005 x 40000004 x 40000003 x ... 2 x 1

10! = 3628800, two trailing zeros

16! = 20922789888000, three trailing zeros

Hint: You do not have to multiply to get the answer.

[ProudFossil]

Another interesting, but less useful trick than the rule of 11. (How offen do you need to multiply by 11 anyway?) What’s the square root of: 12345678987654321 ?

Isn't it half of 222,222,222?

[bvw]

Is the “it” that was immediately obvious the same as the “it” you saw? I have to ask because you used 2 “it”s. Me, I would have used

1

letting my fingers linger awhile on the button.

[jdsteel]

How offen? Your math skills are great, but your typing skills are weak! ; )

[jdsteel]

How offen? Your math skills are great, but your typing skills are weak! ; )