Solution:

25

Distance between Tribe Q and Tribe S = 40km
=> Distance between Tribe Q and Tribe R + Distance between Tribe R and Tribe S = 40km
=> Distance between Tribe Q and Tribe R + (Distance between Tribe Q and Tribe R - 10) = 40 km
=> 2 * Distance between Tribe Q and Tribe R = 50km
=> Distance between Tribe Q and Tribe R = 25km

Solution:

28 is the required number.

28 * 3 - 2 = 82.

Solution:

16

Explanation:
Let the number be p, then the square will be p^2
According to question:
2p = (p/4) + 7
=> 8p = p + 28
=> p = 4

p^2 = 4^2 = 16.

Solution:

80,000.

Explanation:
The distance traveled by each tyre:
4/5 * 1, 00, 000km = 80,000 km.

Solution:

father:72, Son:27

Explanation:
The only single digit prime numbers are 2, 3, 5 and 7.
Let us use the possible combinations and check when the difference comes to be 45.
Son = 23, Father = 32, Difference = 7
Son = 25, Father = 52, Difference = 27
Son = 27, Father = 72, Difference = 45

This stand apt for the requirements. Thus the present age of the father is 72 years and that of son is 27 years.

Solution:

19

Explanation:
77 empty bottles = 15 full bottles + 2 empty bottles
15 full bottles will give him 15 empty bottles more.
15 + 2 = 17
17 empty bottles = 3 full bottles + 2 empty bottles
3 full bottles will give him 2 empty bottles more.
3 + 2 = 5
5 empty bottles = 1 filled bottle

15 + 3 + 1 = 19

Thus we will be able to get 19 full bottles of soft drink.

Solution:

Box A has five balls and Box B has seven balls.

Solution:

The number is 281.

Solution:

18

Explanation:
Number of days with snow in morning and clear afternoon = A
Number of days with clear morning and snow in afternoon = B
Number of days with no snowfall in morning or afternoon = C

Now, number of days with snowfall = A + B = 13
Number of days with clear mornings = B + C = 11
Number of days with clear afternoons = A + C = 12

Adding these three equations, we get

2 * (A + B + C) = 36
Or, A + B + C = 18

Therefore, they spent eighteen days in total at their vacation.

Solution:

Assuming that John has A number of apples and Jacobs has B number of apples.

As per the question,
A + 1 = B - 1
=> B - A = 2 ------ (p)

Also, A - 1 = (B + 1) / 2
=> 2A - B = 3 ------ (q)

Solving (p) and (q)
A = 5 and B = 7

Therefore, A has 5 chocolates and B has 7 chocolates right now.