Peter drank 2/5 of a quart of milk. Harry drank 6/7 of a quart. How much more of a quart did Harry drink?
$${\frac{{\mathtt{2}}}{{\mathtt{5}}}} = {\mathtt{0.4}}$$
$${\frac{{\mathtt{6}}}{{\mathtt{7}}}} = {\mathtt{0.857\: \!142\: \!857\: \!142\: \!857\: \!1}}$$
$${\frac{{\mathtt{6}}}{{\mathtt{7}}}}{\mathtt{\,-\,}}{\frac{{\mathtt{2}}}{{\mathtt{5}}}} = {\frac{{\mathtt{16}}}{{\mathtt{35}}}} = {\mathtt{0.457\: \!142\: \!857\: \!142\: \!857\: \!1}}$$
Another way would be to find a common denominator for each fraction an then subtract:
$$\frac{2}{5}=\frac{14}{35}$$
$$\frac{6}{7}=\frac{30}{35}$$
.$${\frac{{\mathtt{2}}}{{\mathtt{5}}}} = {\mathtt{0.4}}$$
$${\frac{{\mathtt{6}}}{{\mathtt{7}}}} = {\mathtt{0.857\: \!142\: \!857\: \!142\: \!857\: \!1}}$$
$${\frac{{\mathtt{6}}}{{\mathtt{7}}}}{\mathtt{\,-\,}}{\frac{{\mathtt{2}}}{{\mathtt{5}}}} = {\frac{{\mathtt{16}}}{{\mathtt{35}}}} = {\mathtt{0.457\: \!142\: \!857\: \!142\: \!857\: \!1}}$$
Another way would be to find a common denominator for each fraction an then subtract:
$$\frac{2}{5}=\frac{14}{35}$$
$$\frac{6}{7}=\frac{30}{35}$$
They are both constipated and drunk so if you use the pythagorean therorem, (a squared + b squared = c squared) you will find that Sally drank the most and that the zombie apocalypse will happen in 2.5273 days. but anyway I don't feel like telling you the answer because you're mean.
