A set (X) of 20 pipes can fill 70% of a tank in 14 minutes. Another set (Y) of 10 pipes fills $\frac{3}{8}$th of the tank in 6 minutes. A third set (Z) of 16 pipes can empty half of the tank in 20 minutes. If half of the pipes of set X are closed and only half of the pipes of set Y are open, and all pipes of the set (Z) are open, then how long will it take to fill 50% of the tank?

X can complete one-third of a certain work in 6 days, Y can complete one-third of the same work in 8 days, and Z can complete three-fourth of the same work in 12 days. All of them work together for $n$ days and then X and Z quit, and Y alone finishes the remaining work in $8\frac{2}{3}$ days. What is $n$ equal to?

The price (p) of a commodity is first increased by k%, then decreased by k%; again increased by k%, and again decreased by k%. If the new price is q, then what is the relation between p and q?

What is the unit digit in the multiplication of $1 \times 3 \times 5 \times 7 \times 9 \times \dots \times 999$?

The petrol price shot up by 10% as a result of the hike in crude oil prices. The price of petrol before the hike was ₹90 per litre. A person travels 2200 km every month and his car gives a mileage of 16 km per litre. By how many km should he reduce his travel if he wants to maintain his expenditure at the previous level?

A question is given followed by two Statements I and II. Consider the Question and the Statements and mark the correct option.

Question: Is $(p + q)^2 - 4pq$, where $p$, $q$ are natural numbers, positive? Statement I: $p < q$. Statement II: $p > q$.

Which one of the following is correct in respect of the above Question and the Statements?