Gmat_mission wrote:
In the multiplication above, # represents a single digit. What digit does # represent?

A. 2
B. 3
C. 4
D. 5
E. 6

We're told that # times 512 equals two thousand and something.
Well, 4 times 512 = two thousand and something.
And 5 times 512 = two thousand and something.
No other digits, when multiplied by 512 will give us two thousand and something

So, let's test 4 and 5 (answer choices C and D)

If # = 4, we get: (4)(510) = 2040 (doesn't meet the condition that the product is 2##0. ELIMINATE C

f # = 5, we get: (5)(510) = 2550.
Perfect! This meets the condition that the product is 2##0.

Answer: D

Cheers,
Brent

Gmat_mission wrote:
In the multiplication above, # represents a single digit. What digit does # represent?

A. 2
B. 3
C. 4
D. 5
E. 6

[spoiler]OA=D[/spoiler]

Source: Princeton Review

We see that when a number in the low 500s is multiplied by a single digit number, the product is in the 2000s. Therefore, that single digit number must be either 4 or 5.

If it's 4, then we have 510 x 4 = 2040. However, this is not correct, given that the pound sign (#) can only represent one unique digit.

If it's 5, then we have 510 x 5 = 2550. We see that the pound sign must be 5.

Answer: D