Answer:
B)140
Step-by-step explanation:
So a line is=180 and the interior angles of a triangle= 180, so I did some manipulations
1. 100 + (5x+5) + <ECD = 180. But we also know that (21x-7) + <ECD=180. With some manipulation we can find that <ECD= 180 - (21x-7), so we can plug that into the other equation
2. Now: 100 + (5x+5) + (180- (21x-7))= 180
3. Solve:
105+5x+180-21x+7=180
112-16x=0
112=16x
x=7
4. Plug x=7 into 21x-7= 140
Answer: C
Step-by-step explanation:
Answer: 29400
Step-by-step explanation:
Let's say x = 15% copper and y = 75% copper
We need 120 kg of a 51% copper alloy.
A) x + y = 120
B) .15x + .75y = 61.2 (which is 120*.51%)
Multiplying A by -.15
A) -.15x -.15y = -18 Then add this to B
.60y = 43.2
y = 72
x = 48
I'd suggest you look at this web page
http://www.1728.org/mixture.htm
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Double Check
48 kilograms of .15% copper = 7.2 kg copper
72 kilograms of .75% copper = 54 kg kg copper
So we have 61.2 kg of copper in 120 kg
61.2 / 120 = .51 = 51%