What has 13 hearts but no other organs?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

By moving exactly three matchsticks can you make the below equation true.It can be solved by 3 ways.

I have feet, but no legs. Which animal Am I?

The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.

Boxes are labeled but all labels are wrong!

You are allowed to open one box, pick one ball at random, see its colour and put it back into the box, without seeing the colour of the other ball.

How many such operations are necessary to correctly label the boxes?

Given below is simple addition with a defined pattern pattern:
7 + 7 = 2
8 + 8 = 4
8 + 5 = 1
6 + 9 = 3
10 + 11 = 9

Can you analyze the pattern and find out the answer for:

4 + 9 = ?

Considering the below equation:

V + II - VI = 10
IV - X + VIII = 20
IV - VII + VI = 30

Then, I + II + III = ?

Find the number of squares in the below picture

What is always in front of you but can’t be seen?

Can you name any English verb that becomes its past tense by simply rearranging the alphabets ?