What does below chemistry rebus means?

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

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

What does this rebus riddle means ?

What number do you get when you multiply all of the numbers on a telephone's number pad?

The two towns are exactly 100 km apart. John leaves City A driving at 30 km/hr and Jacob leaves City B half an hour later driving at 60 km/hr. Who will be closer to City A when they meet?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

Find out the number of circles in the given picture having Illusion

what's the probability of getting a king or a queen from a pack of 52 cards?

There is a wide field of corn. A goose finds its way into the field and starts running. Can you find out till which point the goose can run into the field?

Use the numbers 2, 3, 4 and 5 and the symbols + and = to make a true equation. Conditions: Each must be used exactly once and no other numbers or symbols can be used.