1.  What is the four-digit number in which the first digit is 1/3 of the second, the third is the sum of the first and second, and the last is three times the second ?
A. 1439
B. 1349
C. 1539
D. 1342

Answer: Option B

Explanation:

It is given that the first digit is 1/3 of the second. There are 3 such possibilities

1)1 and 3

2)2 and 6

3)3 and 9

Now, the third digit is the sum of the first and second digits.

1)1 + 3 = 4

2)2 + 6 = 8

3)3 + 9 = 12

It is clear that option 3 is not possible. So we are left with only two options. Also, the last digit is three times the second, which rules out the second option.

Hence, the answer is 1349.