Question

There are $4$ groups with $10$ balls in each group. How many balls are there in total?

Answer 1

One group has $10$ balls.
There are $4$ such groups.
Group $1:10$ balls

Group $2:10$ balls

Group $3:10$ balls

Group $4:10$ balls

We need to add 10 balls 4 times.
10 + 10 + 10 + 10 = 40

So, 40 is the correct answer.