Answer:
4.6
Step-by-step explanation:
To find the square root of a number, you're basically asking "What number times itself will equal this number."
So, what number times itself will equal 21?
The square root of 21 is 4.582575695.
Rounded to the nearest tenth, would be where our first "5" is after the decimal point. Since 8, in the hundredth place is greater than 4, we would round up! Thus, the square root of 21, rounded to the nearest tenth, is 4.6