Quantitative Aptitude - Arithmetic Ability Questions

A sum of Rs 4000 becomes Rs 7000 in 6 years at simple interest. If the rate of interest becomes double of itself, then what will be the amount (in Rs) after 6 years?

The average of 10 numbers is X and one of the number is 38. If 38 is replaced with 19, then what will be the new average?

A work can be completed by 18 boys in 24 days. If 6 boys leave after working for 12 days, then how many days will be needed to complete the remaining work?

Working 10 hours a day, Aman can complete a piece of work in 18 days. How many hours a day should he work so as to finish the work in 15 days?

A, B and C can do a job working alone in 6, 9 and 18 days respectively. They all work together for 1 day, then A and B quit. How many days C working alone will take to complete the remainder of the job?

The radii of two concentric circles are 68 cm and 22 cm. The area of the closed figure bounded by the boundaries of the circles is

A sphere of radius 5 cm is melted to form a cone with base of same radius. The height (in cm) of the cone is

If 40 is 0.05% of x, then what is the value of x?