Solution:

Let us solve this problem with the help of diagonals. We know, that the sides of square are parallel. Therefore, the diagonals should also be parallel. See the picture, the yellow diagonals are drawn for referencing.

See the image, you can easily spot the four triangles highlighted with red color.

Now, in this picture, you can spot 3 blue, 3 green and 2 red squares. You can find four more rectangles but they can't be square as their diagonals are not parallel with our yellow referenced diagonals.

Therefore, total number of squares = 4 + 8 = 12.

Solution:

Set the first switches on for abt 10min, and then switch on the second switch and then enter the room.
Three cases are possible
1.Bulb is on => second switch is the ans
2.Bulb is off and on touching bulb , you will find bulb to be warm
=>1st switch is the ans.
3.Bulb is off and on touching second bulb , you will find bulb to be normal(not warm)
=>3rd bulb is the ans.

Solution:

This puzzle has no answer if you are considering this figure in a 2d domain. However if you follow it on a three-dimensional plane, you can do it like shown in the figure given.

Solution:

In the picture you can find the green matchsticks. We have moved them from the bottom and placed them in the middle. It was a bit tricky but now you have your desired result.

Solution:

Since every bacterium divides into two in two minutes and we know the fact that the dish was half filled with bacteria at 3 pm, after exactly 2 minutes, all will divide into two and will fill the petri dish. Thus, the petri dish will become full at 3:02 pm.

Solution:

Michelangelo juggles the diamonds across while crossing the bridge.

Solution:

Four

three placed flat on the table in a triangle(touching each other) and put the fourth one on top of them in the middle.

Solution:

457730 * 4 = 1830920
(DOLLAR * 4 = QUARTER)

Solution:

7, 4, 6, 5, 8

Solution:

The young lady was presented with a bill which belonged to the elderly woman. She had asked the waiter to collect the bill from her daughter.

Solution:

The Stars