Answer:
8RST. That is, N has thousands digit 8, hundreds digit R, tens digits S, and ones
(units) digit T, which means that N = 8000 + 100R + 10S + T. Suppose that the
following conditions are all true:
• The two-digit integer 8R is divisible by 3.
• The three-digit integer 8RS is divisible by 4.
The four-digit integer 8RST is divisible by 5.
The digits of N are not necessarily all different.
The number of possible values for the integer N is
(A) 8
(B) 16
(C) 12
(D) 10
87
(E) 14
Since 8R is divisible by 3, R must be a multiple of 3. The possible values for R are 3, 6, and 9.
Since 8RS is divisible by 4, S must be a multiple of 2. The possible values for S are 0, 2, 4, 6, and 8.
Since 8RST is divisible by 5, T must be 0 or 5.
The possible values for N are therefore:
8000 + 300 + 00 + 0 = 8300
8000 + 600 + 00 + 0 = 8600
8000 + 900 + 00 + 0 = 8900
8000 + 300 + 20 + 0 = 8320
8000 + 600 + 20 + 0 = 8620
8000 + 900 + 20 + 0 = 8920
8000 + 300 + 40 + 0 = 8340
8000 + 600 + 40 + 0 = 8640
8000 + 900 + 40 + 0 = 8940
8000 + 300 + 60 + 0 = 8360
8000 + 600 + 60 + 0 = 8660
8000 + 900 + 60 + 0 = 8960
8000 + 300 + 80 + 0 = 8380
8000 + 600 + 80 + 0 = 8680
8000 + 900 + 80 + 0 = 8980
8000 + 300 + 00 + 5 = 8305
8000 + 600 + 00 + 5 = 8605
8000 + 900 + 00 + 5 = 8905
8000 + 300 + 20 + 5 = 8325
8000 + 600 + 20 + 5 = 8625
8000 + 900 + 20 + 5 = 8925
8000 + 300 + 40 + 5 = 8345
8000 + 600 + 40 + 5 = 8645
8000 + 900 + 40 + 5 = 8945
8000 + 300 + 60 + 5 = 8365
8000 + 600 + 60 + 5 = 8665
8000 + 900 + 60 + 5 = 8965
8000 + 300 + 80 + 5 = 8385
8000 + 600 + 80 + 5 = 8685
8000 + 900 + 80 + 5 = 8985
There are a total of 30 possible values for N. The answer is therefore (E) 14.
Explanation: