## Bigger than you think

Of all integers, what is the percentage of them that contains the number 3?

ei. 1-10 has one three, 1-100 has 19 three’s…

Archive for April, 2012

Posted by Knightmare under Tom (14 Responds)

Of all integers, what is the percentage of them that contains the number 3?

ei. 1-10 has one three, 1-100 has 19 three’s…

Posted by Zorglub under Tom (15 Responds)

A quadrilateral has sides of length 1,2,3 and 4, not necessarily in that order. How large can its area be ?

Posted by slavy under MathsChallenge (7 Responds)

Find all positive integers N, s.t., from the “N string” 12345678910111213….N with the help of (unlimited number of) “+” signs we can derive 2013.

Example: We can derive 28 for N=4 via 1+23+4

Posted by Chris under MathsChallenge (18 Responds)

Here’s one from Slavy.

All the numbers from 1 to 2012 are written in a string,

i.e. 123456789101112…..20112012. You are given as many pluses “+” as you wish, that you are allowed to place anywhere in the string. For a given positive integer n, greater than 1, in how many different ways can you place the + [...]

Posted by Chris under Logic (5 Responds)

During a game of dice, a spectator decided to keep track of the rolls. He recorded the product of the rolls. For example: a roll of 4 and 5 is scored as 20.

1st roll score – (we do not know)

2nd roll score – 5 more than the 1st roll score

3rd roll score – 6 less [...]

Posted by Chris under Tom (7 Responds)

posted on behalf of jenny.

a rich guy lives in a round house and goes out one day. when he comes back his son’s been murdered. he goes up to his baker and asks did you kill my son. the baker says no and that he has been baking cupcakes. the man goes up to to [...]

Posted by Zorglub under Tom (17 Responds)

The earth is spherical with a radius of 6400 km.

A long chain is tighten around it. Then, an extra piece measuring 1 m is added to the chain and a point of the chain is pulled perpendicularly away from the earth until the chain is tight again. What is the distance between the earth and [...]

Posted by ragknot under Tom (18 Responds)

In the Antarctic, below frozen ice sheets I saw things I thought were very odd. Beginning at the bottom of the floating ice sheet, traveling to the sea floor were “branches” of ice. These branches had smaller “limbs” that were also pointed downward. They had small pieces that looked like small fern leaves. Being ice, they were [...]

Posted by Patrick under Tom (11 Responds)

Six post office employees are working today.

It takes one employee one minute to serve one person.

How long would you have to wait in the line if you hold number 321?

Posted by Zorglub under SharedPuzzle (38 Responds)

There are 15 marbles with different colors. Their weight are all different, but the only way to rank them is by using a three-tray scale. The scale accepts exactly 3 marbles, one in each tray, and only indicates which of the three weighs the most, the least and consequently the one in between.

What [...]