In the multiplication above, \(\#\) represents a single digit. What digit does \(\#\) represent?

[Gmat_mission]

In the multiplication above, \(\#\) represents a single digit. What digit does \(\#\) represent?

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

Answer: D

Source: Princeton Review

[ravinikhil]

The final number must be of the form 2 XX0 and must be a divisible by 510.
since both the nos involved have 0 at the end , lets divide both by 10 and get rid of the extra 0's.
thus the no now is 2XX and 51.
now lets just add 51,
51,102,153,204,255.
bingo !
we get 255 which is of the form 2XX.
Hence X is 5.
to verify just put in the pic given, 510 * 5 = 2550 .
should not take more than 30 seconds

[Scott@TargetTestPrep]

2018-11-13_1250.png

In the multiplication above, \(\#\) represents a single digit. What digit does \(\#\) represent?

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

Answer: D

Solution:

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 # must be 5.

Answer: D