how many meiotic divisions are necessary for the formation of 100 grains?? ans-125....please explain how??

For formation of 100 grains, 100 male gametes and 100 female gametes (eggs) are required. 100 male gametes are developed from 100 microspores (from 25 meiotic divisions) and 100 eggs are developed from 100 megaspores (from 100 meiotic division).

Hence, number of meiotic divisions necessary for 100 grains formation = 25 + 100 = 125.