There was a minor accident with a doctor's son but the doctor noticed no major injury. After the treatment, the father of that doctors son is sitting with the son of the doctor without the doctor being in the room.

How can this be possible?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

Pronounced as 1 letter, And written with 3, 2 letters there are, and 2 only in me. I’m double, I’m single, I’m black blue and grey, I’m read from both ends, and the same either way. What am I?

0 0 0 = 6
1 1 1 = 6
2 2 2 = 6
3 3 3 = 6
4 4 4 = 6
5 5 5 = 6
6 6 6 = 6
7 7 7 = 6
8 8 8 = 6
9 9 9 = 6

You can use any mathematical symbols in the space provided to make all above algebraic expressions true.

Sally lives in a place where six months of the year is mild summer and the temperature drops significantly the other six months. She owns a lake where there is a small island. She wants to build a house on the island and needs to get materials there. She doesn’t have a boat, plane, or anything to transport them to the island. How does Sally solve this problem?

Replace the question mark with the correct number in the below-given picture?

How many sides does a circle have?