Solution:

5 questions

Explanation:
This question can be solved using a simple trick. If all the questions were answered correctly, the student would have 200 chocolates.
For every wrong answer, he will lose 5 chocolates and he will also lose 10 chocolates that he would have gained if he would have answered correctly. Thus, for every wrong answer, you have to deduct 15 chocolates from 200.
200 - 125 = 75
15 * 5 = 75
Hence, he gave wrong answer for 5 questions.

Solution:

45

1/5 of 45 = 9
9 + 45 = 54

Solution:

7 Races.

Solution:

Since both of them lied in all three statements, this means that the opposite is true. So the changed statements will be:

Poornima: I am surely over 30.
Riya: I am not 28 and you are at most 4 years older to me.
Poornima: You are at most 28.

Poornima is 31 years old at least as can be concluded from the first statement. Combining the second and the third statement, we can accomplish that Riya is at most 28 years old. Hence, the possible ages of Poornima and Riya can be:

Poornima: 31, 32, 33, 34, 35, 36...
Riya: 22, 23, 24, 25, 26, 27...

Now, reading the second statement again, we can conclude that the difference between the ages of Poornima and Riya is at max 4 years.
This brings us the result that Poornima is 31 years old whereas Riya is 27 years old.

Solution:

Let us denote the number of boys as 'p' and the number of girls as 'q'.

The first statement says that each boy has equal numbers of brothers and sisters
(p - 1) = q
=> p - q = 1 ------- (a)

The second statement says that every girl has twice as many brothers as that of sisters
2 (q - 1) = p
=> 2q - p = 2 ------- (b)

By solving (a) and (b)
We get q as 3 and p as 4.

Therefore, there are 4 boys and 3 girls in the family.

Solution:

18

Explanation:
More minutes implies more tea.
More women implies more tea.

The time become twice (3 minutes / 1.5 minutes).
women become six times (9 / 1.5).

Number of tea = 2 * 6 * Original(1.5)
= 18

Solution:

Let the cost of cap = m
Cost of pen = (5 + m)

As per the condition

5.50 = 5 + m + m
2m = 0.5
m = 0.25

Hence, the cap costs 25 Paise.

Solution:

60 minutes

Explanation:
Roy will be able to consume all the five tablets in an hour.

Tablet 1 will be taken in 0 min.
Tablet 2 will be taken in 15 min.
Tablet 3 will be taken in 30 min.
Tablet 4 will be taken in 45 min.
Tablet 5 will be taken in 60 min.

Solution:

The three numbers are:
-3, -1 and 1.

Solution:

12/27

Explanation:
This is really simple if you know the concept. You just have to increase the fraction by multiplying with a number. In that way, you will increase the numerator and you will be able to find the required fraction. Here, we are multiplying the numerator and denominator of both the numbers with 9. Now if you simplify, the number will remain the same and thus dont think we changed the fraction.

1/3 * 9/9 = 9/27
2/3 * 9/9 = 18/27

Its easy to find the one third fraction on the way now i.e. 12/27.