Solution:

20 paisa coins : 200
25 paisa coins : 124

Explanation:
Say he collect 20-paisa coins be A
Say he collect 25-paisa coins be B
=>number of 25-paisa coins = (324 - A).

Therefore,
0.20 X A + 0.25 (324 - A) = 71
=>20A + 25 (324 - A) = 7100
=>5A = 1000
=>A = 200.

Hence, number of 25-paisa coins = (324 - A) - 124.

Solution:

The answer is very simple. All she had to do is take the fifteen cards from the top and reverse them. This would make another pile out of that and there will be two piles - one of 15 cards and one of 37 cards. Also both of them will have the same number of inverted cards.

Just think about it and if the mathematical explanation will help you understand better, here it is.
Assume that there were p inverted cards initially in the top 15 cards. Then the remaining 37 cards will hold 15-p inverted cards.
Now when she reverses the 15 cards on the top, the number of inverted cards will become 15-p and thus the number of inverted cards in both of the piles will become same.

Solution:

Put one red marble in one box and all other marbles in the 2nd box.

Probability :
50 + 24/49

Solution:

Karate Kid (car + at + tea + kid)

Solution:

3 1 2 2 1 1
1 3 1 1 2 2 2 1

Read Line as one 1 => 1
Read Line 2 as two one => 2 1
Read Line 3 as one two and one one => 1 2 1 1
and so on.

Solution:

2 minutes (duration between 9:59 and 10:01)

Solution:

Treasure Map Is Hidden Inside The Hanging Room Floor.

Explanation.
Just reverse the text "roolF mooR gnignaH ehT edisnI neddiH sI paM erusaerT".

Solution:

A
D
C
A
B

Solution:

Solution can be verified from the picture below.

Solution:

The woman told him to take out one nut each from the rest of the wheels and use them.

Solution:

What is the correct time ?