If there is inequality in the pattern of population growth, there is greater inequality in food production and utilisation. As societies become wealthier, their consumption of animal products increases. This means that a greater proportion of such basic foodstuff as grains and legumes that could feed humans directly is instead being converted into feed for poultry and large farm animals. Yet this conversion of plant-based food into animal food for humans is far from efficient. Only $16 \%$ of the calories fed to chickens are recovered by us when we eat them. This conversion rate goes down to five to seven per cent in large animals that are fed grain to add fat and some protein before slaughter.

$P$ and $Q$ walk along a circular track. They start at 5:00 a.m. from the same point in opposite directions. $P$ walks at an average speed of 5 rounds per hour and Q walks at an average speed of 3 rounds per hour. How many times will they cross each other between 5:20 a.m. and 7:00 a.m.?

If there is inequality in the pattern of population growth, there is greater inequality in food production and utilisation. As societies become wealthier, their consumption of animal products increases. This means that a greater proportion of such basic foodstuff as grains and legumes that could feed humans directly is instead being converted into feed for poultry and large farm animals. Yet this conversion of plant-based food into animal food for humans is far from efficient. Only $16 \%$ of the calories fed to chickens are recovered by us when we eat them. This conversion rate goes down to five to seven per cent in large animals that are fed grain to add fat and some protein before slaughter.

A tram overtakes 2 persons $X$ and $Y$ walking at an average speed of $3 \mathrm{~km} / \mathrm{hr}$ and $4 \mathrm{~km} / \mathrm{hr}$ in the same direction and completely passes them in 8 seconds and 9 seconds respectively. What is the length of the tram?

In only 50 years, the world's consumption of raw materials has nearly quadrupled, to more than 100 billion tons. Less than $9 \%$ of this is reused. Batteries of old vehicles contain materials such as lithium, cobalt, manganese and nickel that are pricey and can be hard to obtain. Supply chains are long and complicated. Buyers' risks are being aggravated by their suppliers' poor environmental and labour standards. Reusing materials makes sense. Once batteries reach the ends of their lives, they should go back to a factory where their ingredients can be recovered and put into new batteries.

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

"A good statesman, like any other sensible human being, learns more from his opponents than from his fervent supporters. For his supporters will push him to disaster unless his opponents show him where the dangers are. So if he is wise he will often pray to be delivered from his friends, because they will ruin him. But, though it hurts, he ought also to pray never to be left without opponents; for they keep him on the path of reason and good sense. The national unity of free people depends upon a sufficiently even balance of political power to make it impracticable for the administration to be arbitrary and for opposition to be revolutionary and irreconcilable."

$\mathbf{X}$ can complete one-third of a certain work in $\mathbf{6}$ days, $\mathbf{Y}$ can complete one-third of the same work in $\mathbf{8}$ days and $\mathbf{Z}$ 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?