Twenty frogs are sitting on a log floating on the surface of a river. Two of them decide to jump off into the water.

How many frogs are there on the log at this moment?

In a university, a professor gave a set of three problems to the three brilliant students of his class. See the image for the questions.

What is the Surname of Barbie Doll?

Without looking at a calendar, within a minute name, a boy's name using 5 consecutive 1st letters of 5 consecutive months

I am green and found in the forest and have needles instead of leaves. What am I?
Hint 1: It can be used for Christmas decorations.
Hint 2: I have a strong, scent that is used in air fresheners.

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

1 + 9 + 8 = ?
considering, 28 + 8 + 92 = 10

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?

Prove that the below maths equation is true.

8 + 8 = 91