20 is greater than 10, because when comparing usual positive whole numbers, the number that is further to the right on the number line is greater.

Quick idea

  • When comparing two positive numbers, the one with the larger value (more units) is greater.
  • On a number line, numbers increase as you move to the right, so 20 lies to the right of 10 and is therefore greater.

Tiny number-line story

Imagine standing on a straight path marked with numbers: 0, 1, 2, 3, … up to 20.

You start at 10 and walk forward to 20; every step you take moves you to a larger number, so the place you end up (20) must be greater than where you started (10).

Simple rule of thumb

  • If both numbers are positive and have different sizes, the one with more digits is usually greater (20 vs 9, 100 vs 20, etc.).
  • If they have the same number of digits, compare them from left to right: in “20” vs “10”, the first digit 2 is greater than 1, so 20 > 10.

TL;DR: Among ordinary whole numbers like 10 and 20, 20 is greater.