Every employee of a firm is given the same flat raise of ₹1,500 a month. Before the raise the mean salary was ₹28,400, the median ₹26,000 and the range ₹42,000. Which statement describes the salaries after the raise?

Adding the same amount to every salary slides the whole distribution along without stretching it. Measures of CENTRE move with it: the mean becomes 28,400 + 1,500 = ₹29,900 and the median 26,000 + 1,500 = ₹27,500. Measures of SPREAD do not, because the highest and the lowest salary both rise by ₹1,500 and the gap between them is untouched, so the range stays ₹42,000 — and the same is true of the interquartile range and the standard deviation. Adding the raise to the range as well gives ₹43,500; leaving the median alone treats it as immune to a shift, which it is not; and the last option supposes that because everyone gained equally nothing changed at all.