a 2.5 metre water tank takes 8 hours to fill 60cms, it loses 20cms per nightit rises by 40cms a day what day will it overflow
That's pretty straight forward. The tank gains a net 40-20 cm per day and night so after the first day and night has 20 cm in it. After the second day and night it has 40 cm. It will be completely filled after the third day, although it will then gain 20 cm each day and lose 20 cm each night after that.