La gran ciudad: De la población de una gran ciudad se sabe que al cabo de un año: de los que comienzan el año allí, 80% se quedan y 20% se van de los que comienzan el año afuera, 90% se quedan afuera y el 10% se mudan a la ciudad. Si se sabe que al cabo del año hay 20 millones afuera y 3 millones adentro, ¿cuáles eran las cantidades de las personas que se quedan y las que se van al comenzar el año?

answer: the answer is (b) amie should have multiplied

step-by-step explanation: given a sphere and a cylinder with same radius and height.

let, 'r' be the radius of the cylinder and sphere and 'h' be the height of the cylinder. according to the question,

r = h.

now, the volume of the sphere will be

and the volume of the cylinder will be

therefore, we have

thus, ammie should have multiplied the volume of the sphere

- "runner b is moving at a slower rate."

- "the graphs shown are graphs of distance(km) against time(min).

the slopes of this graphs are are given by:

slope = (change in y)/(change in x)

= (change in distance)/(change in time)

this is the formula for finding the speed. so, the slope of these graphs represent the speed of the runner.

taking each division in the graph to represent 1 on both axis:

runner a ⇒ speed = (2-0)/(1-0)

= 2/1

= 2 km/min

runner b ⇒ speed = (3-0)/(3-0)

= 3/3

= 1 km/min

this shows that   runner b is moving at a slower rate."