Quick questions on Rates, unit conversions and the unitary method for HSC Maths Standard 2

The reliable way through every rate problem is to carry the units along with the numbers and cancel them like the letters in algebra (a "symbol" you cancel from top and bottom). Set up each calculation so the unwanted units cancel and the unit you want is left. This turns a wordy problem into a single line of arithmetic. It also shows up at once if you have multiplied when you should have divided.

$1$ km = $1000$ m, so converting $5$ km to m gives $5000$, not $0.005$. From larger to smaller the number grows; from smaller to larger it shrinks.

$1$ m$^2$ = $10000$ cm$^2$ (not $100$) and $1$ m$^3$ = $1\,000\,000$ cm$^3$. Squared units need squared factors; cubed units need cubed factors.

A speed in km/h needs the time in hours, not minutes. Convert first.

An answer of dozens of tablets a day signals a unit error. Flag it.