The individuals in a population can be divided into three age groups: pre-reproductive, reproductive, and post-reproductive age groups. The triangular-shaped graph is observed in developing countries as the pre-reproductive population is more there.
In a growing population of a country, pre-reproductive individuals are more than reproductive individuals.
Whenever the population is of a growing or expanding type, the population of pre-reproductive individuals or the younger population is very large. The reproductive population will be moderate whereas the post-reproductive individuals are very few. Thus, the rate of growth will depend on the size of the pre-reproductive population.
Also Read: Human Population
A sphere of radius R is cut from a larger solid sphere of radius 2R as shown in the figure. The ratio of the moment of inertia of the smaller sphere to that of the rest part of the sphere about the Y-axis is : 
AB is a part of an electrical circuit (see figure). The potential difference \(V_A - V_B\), at the instant when current \(i = 2\) A and is increasing at a rate of 1 amp/second is: