A crane has a cable with a breaking strain of 6400 kg measured to 2 significant figures. It is used to lift crates which weigh 90 kg measured to the nearest 10 kg. What is the greatest number of crates that can safely be lifted at one time without breaking the cable? Some working must be shown.

## Step1: Determine the maximum load the crane can support### The crane cable can support a maximum load of .## Step2: Determine the weight of each crate### Each crate weighs .## Step3: Calculate the number of crates the crane can lift### To find the number of crates, divide the maximum load by the weight of each crate: ## Step4: Round down to the nearest whole number### Since the crane cannot lift a partial crate, we round down to the nearest whole number. Thus, the greatest number of crates that can be safely lifted is 71.