¿Qué velocidad inicial hay que comunicar a una piedra para que, lanzándola verticalmente hacia arriba, alcance una altura máxima de 20 m? ¿Cuánto tiempo tardará en alcanzar dicha altura?

i will answer your question if you answer mine

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form