Question

When I ask a person what their life is, I answer: my life is an odd number less than 100, a multiple of 13 and divisible by 3. The life of the person is: a.​

Answer 1

• 39 years

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Let the number be N.

It is less than 100, odd, divisible by 13 and 3.

Since 13 and 3 are mutually primes, N is divisible by 13*3 = 39.

There are 2 multiples of 39 that are less than 100:

• 39 and 78

The second number is even, so we are left with N = 39.

Answer 2

With the study on the classification of numbers we find out the age of the person who is 39.

Classification of numbers :

Odd number: An integer is odd if and only if it can be represented in the form 2n + 1, with n ∈
`\mathbb{Z}`

Multiples of a number are obtained by multiplying that number by successive natural numbers. Multiples of 13 → 13*n, where n is any natural number. Set of multiples of 13: {13*0, 13*1, 13*2,....}

Divisibility criteria :

Divisibility criteria allow you to recognize, without performing division, whether a number is divisible by another. Decomposing a number as a product of its factors. A number is divisible by 3 when the sum of its digits is a multiple of 3.

So let's solve the exercise. The fact that it is divisible by 3 means that it is a multiple of 3 as well, that is, just do the following product 13 x 3 = 39 is an odd number less than 100, multiple of 13 and divisible by 3.