GMAT Counting & Probability practice questions

A research team needs to prepare 1,250 ml of a mixture containing three chemical solutions: A, B, and C. Solution C must constitute 40% of the total mixture, while the remaining volume is divided between Solutions A and B in a 4:1 ratio. How many milliliters of Solution A should be added to the mixture?

A laboratory technician is preparing a series of chemical solutions with concentration levels measured in parts per million (ppm). Solution A has a concentration of 450 ppm, and Solution B has a concentration of 720 ppm. The technician needs to create 1,200 mL of a new solution with a concentration of exactly 600 ppm by mixing these two solutions. How many milliliters of Solution A should be used in the mixture?

A basketball team has won 60% of its first 40 games this season. To finish the season with an overall win percentage of at least 70%, what is the minimum number of additional games they must win out of their remaining 20 games? Assume no ties occur.

A city allocates its budget across three departments: Public Safety, Parks & Recreation, and Public Works. The budget for Public Safety is $30 million, which is twice the budget for Parks & Recreation. The total budget for Parks & Recreation and Public Works is $25 million. What is the average budget allocation per department, in millions of dollars, rounded to the nearest whole number?

A city allocates its annual budget across five departments: Parks $P$, Roads $R$, Schools $S$, Utilities $U$, and Public Safety $PS$. The budget shares are allocated in the ratio P:R:S:U:PS = 3:5:4:2:6, respectively. If the total budget is $40 million, and the Roads allocation is later reduced by 20% to fund a new Traffic Management initiative, what is the difference (in millions) between the largest and smallest allocations after this change?