Quantitative Aptitude - Arithmetic Ability Questions

The brother is elder to his sister by 6 years. Seven years ago the product of their ages was 72. What is the age of the brother?

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

If √(1 - sin2A) = x, then the value of x is

If O is the orthocentre of a triangle ABC and ∠BOC = 100°, the measure of ∠BAC is

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?

Ram is 20 years younger than Shyam. 5 years ago, the ratio of their age was 3:5. The sum of their present age is

A student multiplied a number by 3/10 instead of 10/3. What is the percentage error in the calculation?

Find the LCM of 3.2, 2.72, 1.28 and 1.44