A pipe can fill a cistern in 30 minutes and a waste-pipe can empty it in 1 hour. If both pipes are opened at once when the cistern is empty, how long will it take to fill the cistern?
plz plz solve it..I am confused

answer:

30 minutes

Step-by-step explanation:

There giving you extra information to confuse you but its ok

when rotating a figure 180 degrees, imagine that you are able to take the figure and turn it clockwise or counterclockwise around a center point. to rotate a figure 180 degrees, you will need to apply the rule (x, y) → (-x, -y). start by using a coordinate grid with coordinates for each vertex of the figure. the center point of the coordinate grid is located at (0, 0), which is what you will rotate the figure around. write down the original coordinates of the shape you are going to rotate. then, apply the rule. for example, coordinate (1, 2) becomes (-1, -2). another example would be, coordinate (-4, -2) becoming (4, 2). after you change each original coordinate to the rotated coordinate, you will draw your new figure.

step-by-step explanation:

not sure but it may be b, as i said i'm not sure.