Let X = the 29% alloy and Y = the 60% alloy.
They want a total of 80kg, so you have X +Y = 80
Rewrite that to get X = 80-Y
You also want 0.20X + 0.60Y = 0.52(80)
Replace X with 80-y:
0.20(80-y) + 0.60y = 0.52(80)
Simplify:
16 - 0.20y + 0.60y = 41.6
Combine like terms:
16 +0.40y = 41.6
Subtract 16 from each side:
0.40y = 25.6
Divide both sides by 0.40
y = 25.6 / 0.40
y = 64
Now you have Y replace y with 80 in X = 80-Y
X = 80 - 64
X = 16
They need 64 Kg of the 60% alloy and 16 Kg of the 20% alloy.
2x^2 + x + 3=0 has only complex roots.
The determinant is 1-4*2*3 = -23
-23 (or any determinant) is the part under the square root sign, If that determinant is negative, knowing you cannot take the square root of a negative number, we know the answers must be complex.
multiplying both sides by x^2
simplifying
dividing by 7
15 electricians worked for 24 days to the whole job, now, there are 15 of them, so on any given day, each electrician worked one whole day, in 24 days, that one electrician worked 24 days total.
now, there were 15 electricians on any given day though, since each one of them worked the whole day that one day, so the "days work worth" on a day is 15, so the house gets 15days worth of work because of that.
so how many "days worth" did all 15 do on the 24 days, well, 15+15+15+15+15+15+15+15+15+15+15+15+15+15+15+15+15+15+15+15+15+15+15+15, namely 15 * 24, or 360 days worth of work.
since it takes 360 days worth of work to do the whole wiring, in how many days would 18 electricians do it? 360/18.
C. 3/2 divided by 3
Alina has 3/2 hours to complete her homework. She should divide her 3/2 hours by the 3 assignments to determine how much time she will spend on each assignment. This turns out to be 1/2 hours, or 30 minutes, on each assignment. 3/2 hours is the same thing as 90 minutes, so this answer makes sense. We want the time to be divided by the number of assignments, not vice versa.
