Can you solve this picture maths equation?

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

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

Count the number of triangles in the given picture.

Only one color, but not one size,
Stuck at the bottom, yet easily flies.
Present in sun, but not in rain,
Doing no harm, and feeling no pain.
What is it?

You are given four results as below:
1111 = F
2222 = E
3333 = T
Then, can you find out how to code 4444?

No matter how little or how much you use me, you change me every month. What am I?

One of the leprechaun is missing if you see the two pictures attached to this question. Where did he go? When he comes back, do you know where has he been?

You need to remove four matchsticks from the picture below and still need to maintain the following as in the original image.
1. 1st row contains 12 matchsticks
2. 2nd row contains 12 matchsticks
3. 1st column contains 12 matchsticks
4. 2nd column contains 12 matchsticks

Why is the Hole below a Lock?

what one word does the below rebus identifies?