In April, the profit of a book store is increased by 25%, and in May, it is decreased by 20%. How did the profit of the store at the end of May compare to that in the beginning of April?
A can finish a piece of work in 20 days and B can finish it in 24 days. They work together for 10 days then A leaves. In how many days will B finish the remaining work?
Name the British chemist who presented his atomic theory in 1808, on conservation of mass and law of definite proportions, which was a turning point in the study of matter.
