# A box contains 36 tins of cleaning powder. Each tin contains 225 g of the powder, and the tin itself has a mass of 15 g. If the full box has a mass of 10 kg, what is the mass of the empty box?

Dec 14, 2016

The mass of the empty box is 1 kg.

#### Explanation:

$\text{Mass of each tin" = "mass of powder + mass of tin" = "225 g + 15 g" = "240 g}$

$\text{Mass of 36 tins" = 36 color(red)(cancel(color(black)("tins"))) × "240 g"/(1 color(red)(cancel(color(black)("tin")))) = "8640 g}$

8640 color(red)(cancel(color(black)("g"))) × "1 kg"/(1000 color(red)(cancel(color(black)("g")))) = "8.64 kg"

$\text{Mass of full box = mass of box + mass of tins}$

$\text{10 kg = mass of box + 8.64 kg}$

$\text{Mass of box" = "10 kg - 8.64 kg" = "1.36 kg" = "1 kg}$

Note: According to the rules for significant figures, we are not allowed to carry any digits past the decimal point.