In a district, two schools have 48,600 and 37,400 students respectively

Why

Ankit's rounding is a genuinely smart way to get a QUICK sense of the total, and 90,000 is a perfectly reasonable ballpark. Where he goes wrong is calling that ballpark 'exact.' Add the real numbers directly: 48,600 + 37,400 = 86,000. His rounded estimate of 90,000 overshoots the true total by 4,000, because he rounded both numbers UP (48,600 to 50,000 added 1,400; 37,400 to 40,000 added 2,600), so both errors stacked in the same direction instead of cancelling out. Rounding is a genuinely useful tool for checking whether an exact answer feels roughly right, and for quick mental estimates — but it is a substitute for exactness only when you don't need the exact number, and a district planning exactly how many textbooks or desks to send needs 86,000, not 90,000. Test: add 48,600 and 37,400 on paper, digit by digit, and compare to the rounded guess — the 4,000 gap is real and would matter for anyone actually ordering supplies. No, that is only an estimate: 48,600 + 37,400 = 86,000 exactly, and rounding both numbers up before adding pushed the estimate 4,000 higher than the true total.