The error bars are used to indicate the variability of the data presented in a graph.
There are several quantities that can be used to generate error bars in the graph. These are:
standard deviation
standard error
confidence interval
Usually, one standard deviation above and below the mean is used although it is advised to indicate which variability data is used to generate the error bars in the graph since the 3 quantity given are not equal.
We do like the following:
Set the first number is a and the second is b.
We have two equations: a+2xb=24, 2xa+b=21
And we have 2xa+4xb=48 or 2xa=48-4xb
So: 48-4xb+b=21 or -3xb=21-48=-27 and we got b=-27:(-3)=9 and a= 6
a=6 and b=9
One foot is defined as 0.3048 meters.
or 12 * 12 = 144
or 12 * 12 * 12 = 1728