A stall's takings on seven days were ₹320, ₹350, ₹360, ₹380, ₹400, ₹410 and ₹1,000. The owner describes a typical day by striking off the best day and the worst day and averaging the other five. By how many rupees is that figure below the mean of all seven days?

The seven days add to ₹3,220, so the plain mean is 3220 ÷ 7 = ₹460. Striking off ₹320 and ₹1,000 leaves 350 + 360 + 380 + 400 + 410 = ₹1,900 over five days, a trimmed figure of ₹380. The gap is 460 − 380 = ₹80. Striking off only the ₹1,000 day would leave 2220 ÷ 6 = ₹370 and the wrong gap of ₹90; the other two options are the two averages themselves. Notice that ₹380 is also the median: the single huge day is what lifts the plain mean to ₹460, a figure that beats six of the seven days.