When it's bad luck to meet a black cat?

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?

If in a code language, DISTANCE is written as IDTUBECN and DOCUMENT is written as ODDVNTNE, the how will THURSDAY be coded as in the same language?

What does it mean?

On her drawing table, Sayna lit 12 coloured candles. A few seconds later she blew two candles off.

How many candles Sayna have at the end?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

I have teeth but i don't bite. Who Am I ?

Can you count the number of triangles in the given figure?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

A mathematics teacher took exams for his students. Out of the total students, 25% passed both the tests included in the exam. However, only 42% were able to clear the first test.

Can you find out the percentage of those students who passed the first test and also passed the second test?