I put forward a geometrical solution.

Now he can join the planks at these angles . And place them accordingly to make the trinagle.

Then he can walk through the planks and reach the island.

Let’s generalize a formula for mxn chess board( given n<m).

So total no. of elements in the chess board would be squares.
So, m*n.
Then we will select 2*2 squares, which will be (m-1)*(n-1).
.
.
.
On further repeating , we will get that:
Total no. of squares= Σ(i=0 to i=n-1) (m-i)*(n-i)

We can mark all the sides of the second sides with 0,0,0,0,0,6,
We have to get the numbers from 1 to 12 to be generated as sum of the no.s appearing on the dice.

By doing this , we get that:
1 -> (1,0)
2 -> (2,0)
3 -> (3,0)
4 -> (4,0)
5 -> (5,0)
6 -> (6,0)
7 -> (1,6)
8 -> (2,6)
9 -> (3,6)
10-> (4,6)
11-> (5,6)
12 -> (6,6)

Every no. has an equal probability of appearance as sum of the no. on the dice.

Probability:

Total combinations possible:

6C1 * 2C1 = 12

Probabilty= 1/12

Hope it helps!!

8

Friday

May be the truck was stuck because the boy and girl were crossing the road. When they crossed, the truck crossed the bridge.

It can also be done in 3-d( as dimension parameter has not been provided)

u

We can solve it mathematically.
Let’s assume that  x,y,z chocolates from 1st, 2nd and 3rd stores respectively.

Now, 0.05x + y + 5z= 100
Which simplifies to x + 20y + 100z= 2000

Now, x + y +z = 100

Subtracting we get,
19y + 99z = 1900

y= 100- 99z/19

Now, Z= 19 only.
y=1
x=80