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If b = 8d - c, and a = d/3, what is the average of a, b, c and d? (A)
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11 Feb 2022, 09:29
11 Feb 2022, 09:29
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If b = 8d - c, and a = d/3, what is the average of a, b, c and d?
(A) 4a
(B) 7a
(C) a/7
(D) 4a + 7
(E) a/7 + 5
(A) 4a
(B) 7a
(C) a/7
(D) 4a + 7
(E) a/7 + 5
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Re: If b = 8d - c, and a = d/3, what is the average of a, b, c and d? (A)
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11 Feb 2022, 10:44
11 Feb 2022, 10:44
1
Carcass wrote:
If b = 8d - c, and a = d/3, what is the average of a, b, c and d?
(A) 4a
(B) 7a
(C) a/7
(D) 4a + 7
(E) a/7 + 5
(A) 4a
(B) 7a
(C) a/7
(D) 4a + 7
(E) a/7 + 5
When I scan the answer choices, I see that all of the answer choices are in terms of the variable a.
This tells me I need to express each variable in terms of a.
For example, we can take the equation a = d/3 and multiply both sides by 3 to get: d = 3a
Now take: b = 8d - c
Add c to both sides: b + c = 8d
Divide both sides by 8 to get: d = (b + c)/8
Since we already know that d = 3a, we can replace d with 3a in the above equation to get: 3a = (b + c)/8
Now multiply both sides of the equation by 8 to get: 24a = b + c
Average of the four values = (a + b + c + d)/4
Substitute to get: average = (a + 24a + 3a)/4 = 28a/4 = 7a
Answer: B
gmatclubot
Re: If b = 8d - c, and a = d/3, what is the average of a, b, c and d? (A) [#permalink]
11 Feb 2022, 10:44
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