Suraj Sood

Hi! (First time posting on the forum.) I'm currently studying for the GRE General Test. Here are some problems I can't seem to figure out: Any help would be very much appreciated! 1. [Quantity Comparison] Every student who took history test H is a junior or a senior. The ratio of juniors to seniors who took history test H is 7 to 5. The average (arithmetic mean) of the seniors who took history test H is 86, and the average of all the students who took history test H is 79. Quantity A: The average (arithmetic mean) score of the juniors who took history test H Quantity B: 73 A) Quantity A is greater. B) Quantity B is greater. C) The two quantities are equal. D) The relationship cannot be determined from the information given. 2. ["Mixtures"] A lab technician needs 40% solution of a certain chemical for an experiment, but the lab she works in only has a 20% solution and a 50% solution in stock. In what ratio should she mix the 20% solution with the 50% solution in order to obtain the 40% solution that she needs? A) 1:3 B) 1:2 C) 2:3 D) 2:1 E) 3:1 (EDIT: I *think* I've reached the right answer for this, but I did end up with a weird negative sign on my ratio.) Thanks in advance! :)