Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

What can you catch but never throw?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

The sum of a mother, her baby and her dog's weight is 170 Kg. How much does the baby weigh if the mother weighs 100 kg more than the combined weight of the baby and the dog, and the dog weighs 60 per cent less than the baby?

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?

There are five vowels (a, e, i, o, u) in the English language.
Can you tell us a word that contains all these vowels?

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

Find three numbers such that When we multiply three numbers, we will get the prime numbers. The difference between the second and the first number is equal to the third and second.

On a certain day, John celebrated his birthday. Two days later, his older twin brother Jacob celebrated his birthday.

Is this even possible? How can it be?