## Task 2 - 070512

A district planned to renovate three streets. The first street is 8 km long, the second is 7 km long, and the third is 6 km long. For each kilometer, 3000 MDN in costs were planned.

One of the three streets was only slightly damaged, so that only half the cost per kilometer was required, while the planned amount was used for each of the other two streets. The total costs for the renovation amounted to 51000 MDN.

For which of the three streets was the planned amount not used?
If all streets had been completely renewed, the costs would have been

$$
(8+7+6) \mathrm{km} \cdot 3000 \frac{\mathrm{MDN}}{\mathrm{km}}=63000 \mathrm{MDN}
$$

Since only 51000 MDN were required, the difference 63000 MDN - 51000 MDN $=12000$ MDN remained. Since a street only incurred costs of 1500 MDN per kilometer, this must be $\frac{12000}{1500}=8 \mathrm{~km}$. The third section required only half the costs.