The first six

What is the smallest positive integer that is divisible by each of the first six positive integers?


The answer is 60.

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2 solutions

Denton Young
May 24, 2016

The first six positive integers are 1, 2, 3, 4, 5 and 6.

Any positive integer is divisible by 1.

if a number is divisible by 4, it is also divisible by 2.

If a number is divisible by 2 and by 3, it is also divisible by 6.

So we need a number divisible by 3, 4 and 5, which are mutually coprime. The smallest such number is 3 * 4 * 5 = 60.

Moderator note:

Simple standard approach.

How does this number grow as we increase the number of initial positive integers that divide it?

Every time you hit a prime, it goes up a factor of that prime. Every time you hit a prime power, it goes up by one factor of that prime.

Denton Young - 5 years ago
Steven Chase
Nov 30, 2016

That's probably why the Babylonians used it as their base.

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