Question

There are 150 coins all are initially heads up, and there are 150 people each person will flip the coin( if head than changes to tail and vice versa) in a manner which is:- 
1st person will flip all the coin 
2nd person will flip coins numbered 2 4 6 8. .159 
3rd person will flip the coin numbered as 3 6 9 12.. . 150 
. 
. 
150th person will flip only 150th coin 

After all this what will be the number of coins with heads up​

Answer 1

Answer:

3

Step-by-step explanation:

Answer 2

Answer:

2, 3, 5, 6, 7, 10, 11, … will have heads facing upwards.

Step-by-step explanation:

The trick is to identify if a coin is being visited by people even or an odd number of times.

Pay attention to the coin number.

Only perfect squares have odd no. of factors, and every other number has even number of factors.

For all those coins which have an odd number of factors will be facing tails upwards and for all those coins which have even no. of factors will be facing heads upwards.

So, coins numbered 1, 4, 9, 16, 25…. will have tails.

2, 3, 5, 6, 7, 10, 11, … will have heads facing upwards.