crackthegmat2011 wrote:Ratio of two numbers a and b is 3:5. If a is increased by 20% and b is increased by 8 then the new ratio becomes 2:5. What is the ratio 2b:(a+6) ?
A) 2:5
B) 3:5
C) 4:5
D) 5:3
E) 10:3
Here's a sneaky approach:
Since the ratio of a:b decreases from 3:5 to 2:5, the 20% increase in
a must be significantly less than 8, the amount that
b is increasing. Thus, the values of
a and
b must be small.
Let's try a=6 and b=10, so that the original ratio is 6:10 = 3:5.
New a = 6 + .2*6 = 7.2.
New b = 10+8 = 18.
New a:b = 7.2:18 = 72:180 = 2:5. This works.
2b:(a+6) = (2*10) : (6+6) = 20:12 = 5:3.
The correct answer is
D.
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