wow !

Once the first person finds a seat, remaining all people will sit in sequence. so, the 49th person can either sit on the seat allocated to 50th person or somewhere else.

Based on where he sits, the last person i.e. 50th person will have 2 options – sit on the 50th seat or somewhere else.

Hence probability is 1/2.

Tea bag

1. Start both the timers
2. Once 4-min timer ends, flip it
Elapsed Time – 4 minutes

3. Once 7-min timer ends, flip it. There will be 1 min. remaining in 4-min timer.
Elapsed Time – 7 minutes

4. Once 4-min timer ends, there will be 6 min. remaining in 7-min timer. Flip 7-min timer
Elapsed Time – 8 minutes

5. When 7-min timer ends, total elapsed time will be 9 minutes.

A centipede lying on its back .. with its feet in the air!

Divide the 100 coins into 2 groups
Group1 with 20 coins

Group2 with 80 coins.

Assume that Group2 has 15 coins are showing tails,
Hence in Group1, 5 coins will show tails, 15 coins will show heads (there are total 20 coins showing tails)

Flip all the coins in Group1 – so now, 15 coins will be showing tails which is the same number as in Group2.

Empty !

Take 1 coin from the first bag, 2 coins from the second bag . . . 10 coins from the tenth bag and simply weigh the picked coins together !

If there are no fake coins, then the total weight should be 110 grams – (1+2+3+4+…9+10)

if bag 4 has fake coins, then the weight will be 110.4 grams.

Heart

Railway line