What four weights can be used to balance from 1 to 30 pounds?

I go up and I go down.
I go up towards the beautiful sky and down toward the green ground.
I am present tense.
I am past tense too
Children love me.

Who Am I?

What kind of band never plays music?

Can you count the number of lines in the below picture?

What can you serve, but never eat?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?

What can jump higher than a building?

John was working on a Chemical Mixture whose weight comprise 90% liquid and 10% solid. The total weight of the mixture is 20 pounds. After a while, John noticed that some of the liquid evaporated and now the liquid comprises just 50% of the weight.

What is the weight of the chemical mixture now?

Two friends were betting. One said to the other, "The coin will be flipped twenty times and each time the coin lands on the head, I will give you $2 and each time it lands on the tale, you will give me $3." After flipping the coin twenty times not a single penny was exchanged among them.

How many times did the coin land on heads?

Can you place six matchsticks in a manner that each of the matchsticks is in touch with the other five matchsticks?