What is the average height of the class?
I. Average height of the class decreases by 1 cm i we exclude the tallest person of class whose height is 56 cm.
II. Average height of the class increase by 1 cm if we exclude the shortest person o the class whose height is 42 cm.

Given that their salaries are in the ratio of 3:4 and expenditure is in the ratio of 4:5 hence we can assume that salary of A and B are 3x and 4x and their expenditures are 4y and 5y.
Now we need to find the ratio of (3x - 4y)/(4x - 5y)
Consider statement I alone:
Giving of B is 25% of his salary hence his expenditure must be 75% so 3/4(4x) = 5y or 3x = 5y from this we can find the required ratio hence this statement is sufficient.
Consider statement II alone :
Given that 4x = 2000 or x = 500 but from this we can not find the value of y and hence we can not find the ratio of their savings.

Consider Statement I alone
Given that Area (?ABC) = Area(?PQR) since nothing about the sides or angles is mentioned, we can not say if they are congruent.Hence, I alone is not sufficient.
Consider Statement II alone
?ABC and ?PQR are right triangles. Nothing about the sides is given, Hence, II alone is not sufficient. Now using both I and II
Now we have two right angled triangle k with same area we may have different combination as only product of base and height is same. Hence even by using both the statement we can not find the answer.

If we look at statement I then we will get
If a = 3 and b = 2, a + b > 0. Here b > 0
If a = 3 and b = -2, a + b > 0. Here b < 0
Hence I alone is not sufficient.
Now if we look at Statement II only then we will get
if a = 3 and b 2, a - b > 0. Here b > 0
If a = 3 and b = -2, a - b > 0. Here b < 0
Hence II alone is not sufficient.
Now by using statements I and II together
If a = 3 and b = 2, a - b > 0 and a + b > 0. Here b > 0
If a = 3 and b = -2, a - b > 0. and a + b > 0. Here b < 0.
Hence I and II together are also insufficient.

If we look at Statement I
i = p - 17 and r = p - 103
Hence, we cannot ind how many each received so this statement is not sufficient enough.
Now by considering Statement II alone.
p + i + r = 170
Hence, we cannot find how many each received. so, this statement is not sufficient enough.
Using I sand II together, we get the value of p and the value of q and r.

If we look at Statement I
It is given that the circle are concentric. But nothing is given about their dimensions. Hence I alone is not sufficient.
In statement II ratio of area is given hence we can find the required ratio.

Given that Ram > Shyam, Vikram > Jay.
Hence from this we can conclude that neither Ram nor Vikram is the shortest. And we have to find the shortest. And we have to find the shortest among them:
Consider statement alone:
We know that that Ram is not the shortest, either Shyam or Jay is the shortest.
Hence (I) alone is not sufficient.
Consider statement I alone Shyam > Vikram.
From the given information and the information in (II), we get Ram > Shyam > Vikram > Jay.
Hence, (II) alone is sufficient.

Given relationship is (PQ)(RQ) = XXX
Since X can take 9 values from 1 to 9 hence we have 9 possibilities
111 = 3 x 37 444 = 12 x 37 777 = 21 x 37
222 = 6 x 37 555 = 15 x 37 888 = 24 x 37
333 = 9 x 37 666 = 18 x 18 999 = 27 x 37
But out of these 9 cases only in 999, we get the unit's digit of two numbers the same. Since it is a unique value, hence we need neither statement I nor statement II to answer the question.

Statement I alone is sufficient.
Statement II alone is not sufficient, for we can have more then one value of MN possible.

From statement I,
E + B < A + D, we easily say that E is less than A, because B>D and as the statement suggest E + B < A + D.
? E < A.
? A is not the smallest integer.
Statement I is sufficient to answer.
From statement II, D < F
This statement is not sufficient to find the relation between A and E.

The data in Statement I, II and III together are necessary to answer the question .