## 86. Math Puzzle $7 / 72$

The water tank of the LPG contains $1000 \mathrm{~m}^{3}$ of water and can be filled by two pumping stations in two days, provided no water is consumed. One pump delivers $300 \mathrm{~m}^{3}$ more water per day than the other.

How many days can the LPG withdraw $400 \mathrm{~m}^{3}$ of water daily if the larger pumping station is out of service?
Pump performance

larger pump: $x+300 \mathrm{~m}^{3} /$ day; smaller pump: $x \mathrm{~m}^{3} / \mathrm{day}$

Filling condition $(x+300+x) \cdot 2=1000 ; \quad x=200$ (2 days)

Balance in $t$ days, if the larger pump fails $1000+100 t$ (supply) $=400 t$ (withdrawal); $\quad t=3$

The LPG can withdraw $400 \mathrm{~m}^{3}$ per day from the water tank for 3 days if the larger pump fails.