An elephant drinks 225 liters of water per day, then in 2 days it drinks 2*225 = 450 liters, in 3 days it drinks 3*225 = 675 liters.
time (days) | 1 | 2 | 3
water (L) | 225 | 450 | 675
If an elephant drinks more water per day, the number of days the water supply lasts decrease. Then these two variables are inversely proportional.