# Number system question

• Jan 29th 2011, 01:08 AM
vivek_master146
Number system question
Q. If 653xy is divisible by 80 then find the value of x+y.

80 = 8 * 10

So y = 0 (As it is divisible by 10)

Now 3x0 should be divisible by 8. X can be both 2 and 6.

The answer is 6. As per my calculation it can be both 2 and 6. Am i right ?
• Jan 29th 2011, 01:50 AM
alexmahone
Quote:

Originally Posted by vivek_master146
Q. If 653xy is divisible by 80 then find the value of x+y.

80 = 8 * 10

So y = 0 (As it is divisible by 10)

Now 3x0 should be divisible by 8. X can be both 2 and 6.

The answer is 6. As per my calculation it can be both 2 and 6. Am i right ?

65320 is not divisible by 80.
• Jan 29th 2011, 01:53 AM
earboth
Quote:

Originally Posted by vivek_master146
Q. If 653xy is divisible by 80 then find the value of x+y.

80 = 8 * 10

So y = 0 (As it is divisible by 10)

That's correct. (Yes)

Quote:

Now 3x0 should be divisible by 8. X can be both 2 and 6.

The answer is 6. As per my calculation it can be both 2 and 6. Am i right ?
If you have divided 653x0 by 10 you are left with 653x.

Therefore 53x must be divisible by 8.