Answer:
B = (zx/2)+ (qx/2)
Step-by-step explanation:
Slot method
20 options
3 slots
First slot: 20 options
Second slot: 19 options (one used up for 1st slot)
Third slot: 18 (one less than last)
Multiply them
20 times 19 times 18=6840
Answer is 6840 ways
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Let L be the low copper alloy and H be the high copper alloy.
We need 0.15L + 0.60H = 0.42 and L + H = 100
L=100 - H
Substituting this into the second equation for L, we get:
0.15(100-H) + 0.60H = 0.42(H+L)
15 - 0.15H + 0.60H = 0.42(H+100-H)
15 + 0.45H = 0.42(100)
0.45H = 42 - 15 = 27
H = 27/.45 = 60 lbs
Back substitution, L = 40 lbs.
