Can someone explain this to me?
The period of oscillation of the
simple pendulum is (2.62 ± 0.11) s i. e. it lies
between (2.62 + 0.11) s and (2.62 – 0.11) s or
between 2.73 s and 2.51 s. As the arithmetic
mean of all the absolute errors is 0.11 s, there
is already an error in the tenth of a second.
Hence there is no point in giving the period to a
hundredth. A more correct way will be to write
T = 2.6 ± 0.1 s

The magnitude of the amount of energy released by burning a fuel source, measured in energy per unit mass, is called its fuel value. note that the fuel value is the negative of the isobaric specific heat of combustion for the fuel. if all the energy obtained from burning 1.23 pounds of butane with a fuel value of 10.85 kcal/g is used to heat 128.0 kg of water at an initial temperature of 18.3 °c, what is the final temperature? note that 1 lb = 453.6 g.