Answer: 5.56 pounds
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Step-by-step explanation:
k = cost of one knife
s = cost of one spoon
costs are in pounds
12s = cost of 12 spoons
16k = cost of 16 knives
12s+16k = 105.64 pounds is the total cost
We can replace k with 4s because of the phrasing "a knife is 4 times the cost of a spoon". Whatever s might be, quadruple it and it leads us to the value of k.
So,
12s+16k = 105.64
12s+16(4s) = 105.64
12s+64s = 105.64
76s = 105.64
s = 105.64/76
s = 1.39 pounds is the cost of one spoon
k = 4s = 4*1.39 = 5.56 pounds is the cost of one knife
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Check:
1 spoon = 1.39 pounds
12 spoons = 12*1.39 = 16.68 pounds
1 knife = 5.56 pounds
16 knives = 16*5.56 = 88.96 pounds
12 spoons + 16 knives = 16.68+88.96 = 105.64 pounds total
This fully verifies the answer.