Start both the 7-min and 11-min glasses simultaneously. After the 7-min one runs out, turn it upside down and let it continue to run. By the time the 11-min glass runs out (11 min. passed), the 7-min. glass will have run for 4 min. after it was upturned first. Turn it upside down again and continue. It will run out in the next 4 min. , completing 15 min.

5

The number at the centre is the product  (number at top + number at left bottom) x number at right bottom, as below:

(3 + 8) x 4 = 44;  (9 + 7) x 2 = 32

(7 + 8) x ? = 75  => ? = 75 / 15 = 5

MULTIPLE variations (all basically same) are possible. All include opening by white with knight, as follows:

Option A: 1 Na3 e5 2 Nb1   (Knight goes back to original position, restoring all write pieces to original positions)
Option B: 1 Nc3 e5 2 Nb1

(both options involving opening with b-knight) and ‘mirror images’ of the the above two, involving opening with the g-knight.

Moreover, similar knight moves by black also can be combined,

e.g., 1 Nc3  Nc6 2. Nf3 – e5 3. Nb1  Nb8 4. Ng1

It can be ANY irregular, closed shape whose ‘centre’ can’t be determined. (Regular shapes like rectangle, circle etc. can’t be considered because, for such shapes, centre can be determined.)

80 bottles of Dutch wine = 400$
19 bottles of French wine = 9500$
1 bottle of German wine = 100$

Total count: 80 + 19 + 1 = 100 bottles.
Total Amt.:  400 + 9500 + 100 = 10,000$

80 pieces at Shop 1 (5 paise); 19 at Shop 3(Rs. 5) and ONE at Shop 2 (1 Rupee)

80 X 0.05 = 4
19 x 5.00 = 95
1 x 1 = 1

Total Count: 80 + 19 + 1 = 100
Total Amount = 4 + 95 + 1 = 100

By taking a ‘tea’ (T) off the Tea-table!

TEA-TABLE, by removing the first ‘T’ becomes  ‘EATABLE‘ or ‘FOOD’

18,000m or 18 km

Since the bug is moving at a constant speed, the distance travelled in any given length of time will remain the same irrespective of how simple or complex the trajectory it follows. Since the speed of the bug is 1m/s, it will travel 60 x 60 x 5  = 18,000 m.

Thinking alphabetically, it’s ‘MOM’ because ‘Mom’ is closer to ‘Kids’ than ‘Dad’ is, in the alphabetical order.
Thinking a bit differently, is ‘Dad’ who is closer – so close that they even share a part of themselves – the ‘d‘ of ‘Dad‘ and ‘Kid‘, whereas ‘Mom’ is not that close – they have nothing in common. 🙂