A stationer buys 500 wall calendars at ₹40 each. He sells 300 of them in December at 20% below cost. At what price per calendar (in ₹) must he clear the remaining 200 in January if the whole lot is to break even?

The lot cost $500\times 40$ = ₹20000. The 300 sold at $40\times 0.80$ = ₹32 brought in ₹9600, so the last 200 must bring 20000 − 9600 = ₹10400, i.e. ₹52 each. (Selling them at cost, ₹40, leaves him ₹2400 short; marking them up by the same 20% he cut, to ₹48, still leaves ₹800 short; and adding the whole ₹2400 shortfall on top of that ₹48 over-recovers at ₹60.)