A rope is 3.5 metres long. A second rope is 240 centimetres long. How much longer is the first rope, in centimetres?
Hints
Take them one at a time. The first gives nothing away.
1A nudge
Put both lengths in the same unit first.
2The strategy
Convert before you subtract, and check the direction of the conversion by asking whether the number should get bigger or smaller. Then check the units the answer is wanted in.
3The full solution
3.5 metres is 350 centimetres, and 350 - 240 = 110 centimetres.
Solution— no shortcut on this one
Convert first: 1 metre is 100 centimetres, so 3.5 metres is 350 centimetres. Now subtract in matching units: 350 - 240 = 110 centimetres. The transferable idea: convert, then calculate, then check the answer is in the unit that was asked for.
Why this is on the test: Unit slips cost marks on questions students can otherwise do, and this one puts the slip in both the conversion and the final unit.