Excretory Products And Their Elimination

The glomerular filtration rate, abbreviated GFR, is the amount of filtrate produced by both kidneys per minute, given as about 125 mL per minute in a healthy person. Working from the figures in NCERT Class 11, Chapter 19 (Excretory Products and their Elimination), the daily filtrate equals 125 mL per minute multiplied by 60 minutes and then by 24 hours, that is 125 x 60 x 24 = 180000 mL, which converts to 180 litres per day. This enormous volume agrees with the textbook statement that the kidneys filter roughly 180 litres daily. The option 1.5 litres reflects the approximate volume of urine actually voided each day after reabsorption, not the total filtrate, so it underestimates the figure massively. The value 7.5 litres is simply 125 mL multiplied by 60 minutes, capturing only one hour rather than a full day. The figure 25 litres has no calculational basis here. Therefore 180 litres is correct. A reabsorption sanity check supports the answer: since nearly ninety-nine per cent of the filtrate is reabsorbed, a 180 litre filtrate logically yields only about 1.5 litres of excreted urine, which is physiologically consistent.