Question

I am a number less than 40. One of my factors is 7. The sum of digits is 8. What number am I?

Answer 1

Answer:

If you're a number less than 40, you're either a two-digit number, or a 1-digit number.

but the other criteria eliminate the possibility of being a 1-digit number. you could either look at all the two-digit numbers less than 40 that have a factor of 7 (namely 14, 21, 28, 35) and by trial and error (or more intelligent first guessing) see which one has digits that add up to 8 (that seems the simpler approach) or look at all the two digits numbers less than 40 whose digits add up to 8 and check which is a multiple of 7 (that gives you a shorter list: 17, 26, 35). If you make both lists, you don't have to do the second check of each method, just look which number is common to both lists

Answer 2

Answer:

Two ways to figure out what number you are:

First way:

The numbers less that 40 which have sum of digits 8 are 17, 26, 35.

Only one of those that has a factor of 7. And that is 35.

So you are 35.

Second way:

The numbers less that 40 which have a factor of 7 are 7,14,21,28,35

Only one of those which has sum of digits as 8. And that is 35.

So you are 35.