**Question: **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?

**Answer:**

The 4 digit number is 1349.

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.