A monkey climbs 30 feet at the beginning of each hour and rests for a while when he slips back 20 feet before he again starts climbing in the beginning of the next hour. If he begins his ascent at 8.00 a.m., at what time will he first touch a flag at 120 feet from the ground?

Clearly, total number of handshakes = (9+ 8 + 7 + 6 + 5 + 4 + 3 + 2+1) = 45.

Let the ten's digit be x. Then, unit's digit = (11 - x).

So, number = 10x + (11 - x) = 9x + 11.

Therefore (9x + 11) + 27 = 10 (11 - x) + x ⟺ 9x + 38 = 110 - 9x ⟺ 18x = 72 ⟺ x = 4.

Thus, ten's digit = 4 and unit's digit = 7.

Hence, required number = 47.

Let the number of cows be x and the number of hens be y.

Then, 4x + 2y = 2 (x + y) + 14 ⟺ 4x + 2y = 2x + 2y + 14 ⟺ 2x = 14 ⟺ x = 7.

Clearly, number of ways of arranging 5 books = 5 ! = 5 x 4 x 3 x 2 x 1 = 120.

So, total time taken = 120 minutes = 2 hours.

Clearly, out of every 16 persons, there is one captain. So, number of captains (1200/16) = 75.

The seven pieces consist of 6 smaller equal pieces and one half cake piece.

Weight of each small piece = 20 g.

So, total weight of the cake = [2 x (20 x6)]g= 240 g.

Income on the first day = Re. 1.

Income on the 2nd day = Rs. (1x2) = Rs. 2¹.

Income on the 3rd day = Rs. (2¹ x 2) = Rs. 2² and so on. Thus, Income on the rath day = Rs. 2^n-1.

Therefore Income on the 10th day = Rs. 2⁹.