Answer:
about 10 days
Step-by-step explanation:
Answer:
There are 165 ways to distribute the blackboards between the schools. If at least 1 blackboard goes to each school, then we only have 35 ways.
Step-by-step explanation:
Essentially, this is a problem of balls and sticks. The 8 identical blackboards can be represented as 8 balls, and you assign them to each school by using 3 sticks. Basically each school receives an amount of blackboards equivalent to the amount of balls between 2 sticks: The first school gets all the balls before the first stick, the second school gets all the balls between stick 1 and stick 2, the third school gets the balls between sticks 2 and 3 and the last school gets all remaining balls.
The problem reduces to take 11 consecutive spots which we will use to localize the balls and the sticks and select 3 places to put the sticks. The amount of ways to do this is
As a result, we have 165 ways to distribute the blackboards.
If each school needs at least 1 blackboard you can give 1 blackbooard to each of them first and distribute the remaining 4 the same way we did before. This time there will be 4 balls and 3 sticks, so we have to put 3 sticks in 7 spaces (if a school takes what it is between 2 sticks that doesnt have balls between, then that school only gets the first blackboard we assigned to it previously). The amount of ways to localize the sticks is
. Thus, there are only 35 ways to distribute the blackboards in this case.
Answer:
<h3> 26²/₃ liters of 15% acid and 13¹/₃ liters of 33% acid</h3>
Step-by-step explanation:
Concentration Amount of Amount
of Solution Solution (L) of Acid
15% x 0.15x
33% y 0.33y
21% 40 0.21•40
x + y = 40 ⇒ x = 40 - y
0.15x + 0.33y = 0.21•40
0.15(40 - y) + 0.33y = 0.21•40
6 - 0.15y + 0.33y = 8.4
0.18y = 2.4
y = 13¹/₃
x = 40 - 13¹/₃ = 26²/₃