Solution:

8 is the required number.

Here, by dividing in half, we will actually chop off the digit from the middle. Then you will be left with two zeroes.

Solution:

Yes it is possible in Roman Numerals. In Roman Numerals,
9 = IX
10 = X
11 = XI

Thus by removing one from 9, you are getting 10 and by removing one from 11, you are getting 10 again.

Solution:

40

Explanation
The number 40 (Forty) is the only number in one million numbers whose letters are arranged in the order they are arranged in English alphabets as well.

Solution:

The pills can run for an hour.

Explanation:
If you had ninety minutes in mind, then you are wrong. You took the first pill at the zero minute. Then you took the second pill after 30 minutes and the third pill after 30 + 30 i.e. 60 minutes or an hour.

Solution:

If you put F over the line that is given, it will become E and form the word SEQUENCE.

Solution:

8

Explanation:
If you look carefully then you will see that five matches lay ahead of the lighter and five are visible in the reflection of the lighter. Out of those five, we can see three matches emerging away from the surface of the lighter but two remains just as a part of reflection. Thus the total number of matches are eight.

Solution:

54325

Explanation:

Consider 1 = 5
2 = 25
3 = 325
4 = 4325
Then 5 = 54325

See the pattern. With every digit, the previous numbers are added after that digit

So the next number in the series is 54325

Solution:

Align the toothpicks to form TEN. Use one toothpick for each of the lines.

Solution:

What

Solution:

Either your read from start or from ends, it will be same