The length $l$, breadth b and thickness t of a block of wood were measured with the help of a measuring scale. The results with permissible errors are $l=15.12 \pm 0.01\; cm , t =5.28 \pm 0.01 \;cm$ $b =10.15 \pm 0.01\; cm$. The percentage error in volume upto proper significant figures is

Write a note on combination of error.

Calculate the mean $\%$ error in five observation

$80.0,80.5,81.0,81.5,82$

The dimensional formula for a physical quantity $x$ is $\left[ M ^{-1} L ^{3} T ^{-2}\right]$. The errors in measuring the quantities $M , L$ and $T$ respectively are $2 \%, 3 \%$ and $4 \%$. The maximum percentage of error that occurs in measuring the quantity $x$ is

If $x=10.0 \pm 0.1$ and $y=10.0 \pm 0.1$, then $2 x-2 y$ is equal to