Pls help I been staring at this and cannot get it right

Suppose there are 10 five and six-year-old attending a birthday party. when a 30 year old mother walks into the room with an infant in her arms, what happens to the mean age in the room? what happens to the standard deviation of ages in the room? a. the mean and standard deviation of both change. b. the meaning will change, but the standard deviation will stay approximately the same. c. i mean will stay approximately the same, but the standard deviation will change. d. the mean and standard deviation will both stay approximately the same.

20 da is equal to a. 2,000 cm. b. 2 m. c. 20,000 cm. d. 20,000 mm

Rob spent 25%, percent more time on his research project than he had planned. he spent an extra h hours on the project. which of the following expressions could represent the number of hours rob actually spent on the project? two answers