Quantitative Aptitude - Arithmetic Ability Questions

P and Q are two alloys which are prepared by mixing tin and lead in the ratio of 12 : 5 and 4 : 3 respectively. If equal quantities of alloys are melted to form athird alloy R, then what is the ratio of tin and lead in alloy R?

From a container of milk, 5 litres of milk is replaced with 5 litres of water. This process is repeated again. Thus in two attempts the ratio of milk and water became 81 : 19. The initial amount of milk in the container was

P and Q can do a project in 150 and 100 days respectively. In how many days can they complete 60% of the project if they work together?

The standard deviation of the set {10, 11, 9, 11, 9} is

If 23x + 23y = 184, then what is the average of x and y?

A and B have to type a book together containing 120 pages. A takes 9 hrs to type 36 pages and B takes 5 hrs to type 40 pages. A typed first 60 pages alone and the last 60 pages were typed by A and B together. How much time (in hours) will be taken to type the complete book?

A, B and C can together do a job in 9 days. C alone can do the job in 36 days. In how many days can A and B do 50% of the job working together?

If a+b=2c then the value of aa-c+cb-c is equal to (where a≠b≠c)