hugomimihu

Arrange your latex properly.

Intresting point.

There are 4 ways of only 1 heads,

HTTT

THTT

TTHT
TTTH

2heads,

HHTT

HTHT
HTTH

THHT

THTH

TTHH
 

3 heads

HHHT
HHTH
HTHH
THHH

4 heads
 

HHHH

0 heads

TTTT

Good point it's 4/16

I'll revise my answer thanks for the correction!

This is an AoPS question, so if you need help feel free to ask during Office Hours(7:30-9:00 EST)

Or ask on the forum.

There's no need to post the question over and over again.

So basically we first need to figure out how much pairs that add to 7.

1,6

6,1

2,5

5,2

3,4

4,3

There are 6*6 = 36 possible outcomes,  so 6/36 = 1/6

See guest's post below for 2).

If you don't understand anything feel free to ask.

There's a total area of 7 squares. 3 on the right are half-covered, so minus 1.5, and the bottom uncovered is half of 4 units, so 2.

2+1.5 = 3.5

7-3.5 = 3.5

We multiply this by 9*9 to get the total.

There are 900 numbers from 1 to 900, inclusive, and 499 from 1 to (500-1) = 499.

I think you can figure out the answer from here.

If you don't understand anything feel free to ask! :)

Also in the future don't put math questions under Off Topic

oh yes don't mind my earlier answer mine is incorrect sorry

GCD is greatest common divisor.

The divisors of 100 are,

1, 2, 4,5,10,20,25,50,100

1,2,4,5, work.

We also have the ones where we multiply something with it.

we have the ones with these numbers as factors.

3, 6,7,8 also works.

Essentially all 1-9 works since the gcd is at least 1 and at most 5.

ask if you don't understand anything.

don't type the first half just type the second half onto here.