Option D is indeed correct, as it ensures that the post's point is equidistant from the ground, maintaining a perpendicular angle at two points on the surface.
2x − y = −4 → 10x − 5y = −20
3x + 5y = 59 → 3x + 5y = 59
13x = 39..... this is derived from adding the two equations on the right.
13x = 39 can be used in place of 3x + 5y = 59 in the initial system and will yield the same result.
Given that the salt concentration in a 125 ml salt solution is at 20%, it indicates a salt to water ratio of 20:80, which simplifies to 1:4.
Consequently, the salt quantity in the 125 ml 20% solution can be calculated as 20% of 125, yielding 0.2 x 125 = 25 ml, and therefore, the water content amounts to 125 - 25 = 100 ml.
When adding 25 ml of water to this 20% salt solution, the total water becomes 100 + 25 = 125 ml while the salt quantity remains at 25 ml.
Thus, the new total volume of the solution is 125 + 25 = 150 ml, leading to a salt proportion in the updated mixture of 25/150 = 0.1667.
As a result, the concentration of the new solution <span>after mixing 25 ml of water with 125 ml of a 20% salt solution is 16.67%</span>
