Solution:

60%

Explanation:
In all such cases where you have to find out the probability of anything with an already given situation, you have to use the formula for conditional probability.

In this case, you have to find out the probability that the second test was passed by a student given that he passed the first test already.

Therefore, P(Second/First) = P (First and Second)/ P (First)
= 0.25/0.42
=0.60
=60 %

Solution:

2/5

Explanation:
This problem can be solved with different approaches. Let us not go into the complicated generic stuff to avoid confusion and try to solve it with simpler means.

Let us find the results separately. There can be 4 different results that give the sum of 5 and there can be 6 different results that give the sum of 7.

Thus, the probability that we get the sum of 4 before the sum of 7 will be:
4/(4+6) = 4/10 = 2/5.

Solution:

There are three roses and four bees.

Solution:

1000

Solution:

I had 10 candies in the beginning.

Explanation:
Let us take and solve this problem in the reverse direction.

At the end, I was left with 1 candy. Let me take the extra one candy back from my younger son. Now since I gave him half of what I had, we must be having the same number of candies. I have 2, which means he also have 2. This implies that I was left with 4 candies after I gave some to the elder son.

Let me take back the extra candy from my elder son now. Now I have 5 candies. Since I gave him half of what I had, he must be having 5 candies as well. Thus, I had 10 candies in the beginning.

Solution:

1/36

Explanation:
The number of possibilities for the first as well as the second dice are 6 and 6 respectively. Therefore the total possibilities or outcome are 6 * 6 = 36.
Out of 36 outcomes, we need only one case i.e. the first gives 2 and the second gives 5.
Therefore, the probability will be 1 on 36 or 1/36.

Solution:

When fifteen minutes have passed, the hour hand has already moved exactly one fourth of an hour. Thus the angle between the hour hand and minute hand will be of 7.5 degrees.

Solution:

If we place a decimal between the numbers it will become 5.9 which is what we needed.

Solution:

5832/17496
This fraction will give the desired result i.e. 1/3.

Solution:

$16