Question

What is the smallest whole number that is equal to seven times the sum of its digits?

Answer 1

Answer:

21

Step-by-step explanation:

Answer 2

21.

Explanation:

The two-digit number ab stands for 10a + b since the first digit represents 10s and the second represents units. If 10a + b = 7(a + b), then 10a + b = 7a + 7b, and so 3a = 6b, or, more simply, a = 2b. That is, the second digit must be twice the first. The smallest such number is 21.