If each of 4 subsidiaries of Corporation R has been granted a line of

Hi All,

In certain Quant questions, you'll be given 'big' numbers to deal with to see if you can take advantage of patterns in the digits (and/or the answer choices) to avoid some of the longer, formal math 'work' and save some time. This is a great, subtle way to 'reward' a critical thinker, which the GMAT does throughout the Test.

Here, you should be quick to notice how there are so many 0s in the math involved. To save some time, we can eliminate 3 or 4 zeroes from the data (and the answers) and perform some simpler calculations.

For example,
[(4)(700) + (3)(112)] / 7

(2800 + 336) / 7
3136/7

From this point, you don't even have to perform the entire calculation - once you realize the answer begins with '44....' you can stop working.

Final Answer:

GMAT assassins aren't born, they're made,
Rich

A Logical way of answering the question in just 20 seconds (this is what I took to answer it ...

Average of 4 Subsidiary = 700_____________________Average of other 3 Subsidiary = 112 (lets take 100 approx)

Average of all 7 Subsidiary would be exactly (700+100)/2=400
But since there are 4 subsidiary with average of 400 so the average must be closer to 700 than 100
i.e. Average must shift towards greater than 400 and the change won't just be 6 (i.e. wont be 406) because we already have taken value of 3 subsidiary lesser than actual value and we are yet to consider one more subsidiary

Hence, Only relevant choice is 448

Answer: Option B

no doubt this is a simple question but I am not sure why we get wrong answer when we take average of first 4 sub (700...). and then avg of 3 sub (112...) and finally take the avg to these two values. (we get 406.... which is option c).
am i missing something ?

Hi jyotipes21,

This question is an example of a "Weighted Average" prompt.

While the average of 700 and 112 is 406, that answer is only correct when we have the SAME number of 700s and 112s. Since we have more 700s than we have 112s, the average of all 7 numbers must be CLOSER to 700 than it is to 112.

GMAT assassins aren't born, they're made,
Rich

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