gmatprep - lightbulbs boxes

Question

see below

eschn3am · Answer

55 bulbs split between 2 boxes
2 bulbs broken in first box
5 bulbs broken in second box

We're really looking for the number of bulbs in the second box.

1. (2*15) = 30 bulbs not broken. Total of 32 bulbs in first box. 55-32 = 23 bulbs in second box. SUFFICIENT
2. x+(x+9) = 55 OR 2x = 46 and x = 23 bulbs in second box SUFFICIENT

Answer D

(just subtract 5 from 23 to get 18 unbroken bulbs in the second box)

maratikus · Answer

First box has 2 broken and x unbroken bulbs
Second box has 5 broken and (55-5-2-x) = 48 - x unbroken bulbs

1) x = 15*2 -> sufficient
2) 2+x = 48-x + 9 -> x can be calculated -> sufficient

D

GMATBLACKBELT · Answer

x+y= box 1 z+n= box2

we know y=2 and n=5

x+2= box 1 z+5= box 2

we also know that x+z+7=55 --> x+z=48

1: x=15(2) --> 30=x thus z=18 Suff.

2: x+2=(z+5) +9 --> x=z+12 thus we can find z --> 2z=36 z=18 Suff.

D

jimmyjamesdonkey · Answer

Agree D. I love these types of problem. I usually setup a tree for them to calculate.

Given:

55 Bulbs
7 Broke
2 Broke in Box 1
Y broke in Box 2
Not Broke Box 1 = a
Not broke box 2 = b
z+y = 7
y = 5

Statement 1:

a = 15*7 Plug back in and solve for b.

Statement 2:

We have two equations

a+2 = 9 + (b+5)
a+2 + b +5 = 55

we can solve for b.

maratikus · Answer

jimmyjamesdonkey, your logic is flawless. however, you might want to be a little more careful with your calculations. 7*15 = 105 > 55, it should've been 2*15.

jimmyjamesdonkey · Answer

good catch. those simple mistakes will get you everytime! good thing this was a DS problem!

gmatprep - lightbulbs boxes

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