[GMAT math practice question]
abcd ≠0, ac = 2:3:4, c:d = 5:6, and a + b + c - d = 42. What is the value of d?
A. 6
B. 12
C. 24
D. 36
E. 48
abcd ≠0, a:b:c = 2:3:4, c:d = 5:6, and a + b + c – d =
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- Max@Math Revolution
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=>
We combine the ratios to form a single ratio for ac:d as follows:
a : b : c = 2 : 3 : 4
c : d = 5 : 6
Multiplying both equations by 5 yields
a : b : c = 10 : 15 : 20
c : d = 20 : 24
and combining them to form a single ratio gives
a : b : c : d = 10 : 15 : 20 : 24
Thus, a = 10k, b = 15k, c = 20k, d = 24k for some number k.
Substituting these values into the expression for a + b + c - d yields
a + b + c - d = 10k + 15k + 20k - 24k = 21k = 42.
Thus, k = 2 and d = 24k = 48.
Therefore, the answer is E.
Answer: E
We combine the ratios to form a single ratio for ac:d as follows:
a : b : c = 2 : 3 : 4
c : d = 5 : 6
Multiplying both equations by 5 yields
a : b : c = 10 : 15 : 20
c : d = 20 : 24
and combining them to form a single ratio gives
a : b : c : d = 10 : 15 : 20 : 24
Thus, a = 10k, b = 15k, c = 20k, d = 24k for some number k.
Substituting these values into the expression for a + b + c - d yields
a + b + c - d = 10k + 15k + 20k - 24k = 21k = 42.
Thus, k = 2 and d = 24k = 48.
Therefore, the answer is E.
Answer: E
Math Revolution
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Score an excellent Q49-51 just like 70% of our students.
[Free] Full on-demand course (7 days) - 100 hours of video lessons, 490 lesson topics, and 2,000 questions.
[Course] Starting $79 for on-demand and $60 for tutoring per hour and $390 only for Live Online.
Email to : [email protected]